diff --git a/front-end/src/pages/professor/course/classroom/ProfessorClassroom.tsx b/front-end/src/pages/professor/course/classroom/ProfessorClassroom.tsx
index 794f644..e524c0d 100644
--- a/front-end/src/pages/professor/course/classroom/ProfessorClassroom.tsx
+++ b/front-end/src/pages/professor/course/classroom/ProfessorClassroom.tsx
@@ -9,7 +9,7 @@ import {
   useTransition,
 } from 'react';
 import { classroomRepository, courseRepository } from '@/di';
-import { useParams } from 'react-router';
+import { useNavigate, useParams } from 'react-router';
 import useModal from '@/hooks/useModal';
 
 import {
@@ -18,20 +18,31 @@ import {
   Reaction,
   ReactionType,
   Requests,
+  RequestType,
 } from '@/core/model';
 import QuestionModal from './components/question/QuestionModal';
 import PDFMainComponent from './components/PDFMainComponent';
 import PDFSideBar from './components/PDFSideBar';
+import ProfessorError from '@/utils/professorError';
 
 export type Action =
   | { type: 'ADD'; payload: Reaction }
   | { type: 'REMOVE'; payload: string };
 
+const SSE_URL = import.meta.env.VITE_API_URL;
+
 const initialReactionsCount = () => {
   const storageCounts = localStorage.getItem('reactions');
   return storageCounts
     ? JSON.parse(storageCounts)
-    : { clap: 0, cry: 0, like: 0, okay: 0, scream: 0, thumb: 0 };
+    : {
+        CLAP: 0,
+        CRYING: 0,
+        HEART_EYES: 0,
+        OKAY: 0,
+        SURPRISED: 0,
+        THUMBS_UP: 0,
+      };
 };
 
 const reactionReducer = (state: ReactionType[], action: Action) => {
@@ -60,17 +71,136 @@ const ProfessorClassroom = () => {
 
   const isUploadingRef = useRef(false);
   const reactionsRef = useRef(reactionsCount);
+  const sseRef = useRef<EventSource | null>(null);
 
   const [isPending, startTransition] = useTransition();
 
   const { openModal, closeModal, Modal } = useModal();
+  const navigate = useNavigate();
+
+  const popupError = ProfessorError({
+    setModal,
+    openModal,
+    closeModal,
+    navigate,
+  });
+
+  const handleReaction = (type: Reaction) => {
+    startTransition(() => {
+      dispatch({ type: 'ADD', payload: type });
+      reactionsRef.current = {
+        ...reactionsRef.current,
+        [type]: (reactionsRef.current[type] || 0) + 1,
+      };
+      setReactionsCount(reactionsRef.current);
+      localStorage.setItem('reactions', JSON.stringify(reactionsRef.current));
+    });
+  };
+
+  const handleRequest = (request: RequestType) => {
+    setRequests(
+      (prev) =>
+        prev.map((req) =>
+          req.type.kind === request ? { ...req, count: req.count + 1 } : req
+        ) as Requests
+    );
+  };
+
+  const handleQuestion = (question: Question) => {
+    setQuestions((prev) => [...prev, question]);
+  };
+
+  const handleQuestionCheck = (id: Question['id']) => {
+    const updatedQuestions = questions.filter((question) => question.id !== id);
+
+    setQuestions(updatedQuestions);
+  };
+
+  const connectSSE = () => {
+    if (sseRef.current) {
+      return;
+    }
+
+    const eventSource = new EventSource(
+      `${SSE_URL}/sse/connection/course/${courseId}`,
+      {
+        withCredentials: true,
+      }
+    );
+
+    eventSource.onopen = () => {
+      sseRef.current = eventSource;
+    };
+
+    eventSource.onmessage = (e) => {
+      const data = JSON.parse(e.data);
+
+      if (data.messageType === 'REACTION') {
+        handleReaction(data.data.type);
+      } else if (data.messageType === 'REQUEST') {
+        handleRequest(data.data.type);
+      } else if (data.messageType === 'QUESTION') {
+        handleQuestion(data.data);
+      } else if (data.messageType === 'QUESTION_CHECK') {
+        handleQuestionCheck(data.data.id);
+      } else {
+        return;
+      }
+    };
+
+    eventSource.onerror = () => {
+      sseRef.current?.close();
+      sseRef.current = null;
+      connectSSE();
+    };
+  };
+
+  // 교수 질문 체크
+  const handleResolveClick = async (id: Question['id']) => {
+    try {
+      await classroomRepository.checkQuestionByProfessor(id);
+      const updatedQuestions = questions.filter(
+        (question) => question.id !== id
+      );
+
+      setQuestions(updatedQuestions);
+    } catch (error) {
+      popupError(error);
+    }
+  };
+
+  //강의 종료
+  const handleCloseClass = () => {
+    if (!courseId) {
+      return;
+    }
+
+    try {
+      sseRef.current?.close();
+      sseRef.current = null;
+      classroomRepository.closeCourse(courseId);
+      navigate('/professor');
+    } catch (error) {
+      popupError(error);
+    }
+  };
 
   // 가장 처음 course 정보 받아오기
   useEffect(() => {
     async function fetchCourse() {
-      const course = await courseRepository.getCourseById(Number(courseId));
-      setCourseInfo(course);
-      setQuestions(course.questions);
+      try {
+        if (!courseId) {
+          navigate('/professor');
+          return;
+        }
+        const course = await courseRepository.getCourseById(courseId);
+        console.log(course);
+        setCourseInfo(course);
+        setQuestions(course.questions);
+        setRequests(course.requests);
+      } catch (error) {
+        popupError(error);
+      }
     }
     fetchCourse();
   }, [courseId]);
@@ -93,84 +223,31 @@ const ProfessorClassroom = () => {
     isUploadingRef.current = isUploading;
   }, [isUploading]);
 
-  //예상SSE 연결
-  // useEffect(() => {
-  //   const eventSource = new EventSource(`sse 주소 `);
-
-  //   eventSource.onmessage = (event) => {
-  //     const data = JSON.parse(event.data);
-
-  //     if (data.type === 'reaction') {
-  //       if (isUploadingRef.current) {
-  //         // isUploading이 true일 때는 우선순위를 낮춰서 처리
-  //         dispatch({ type: 'ADD', payload: data.payload });
-  //         startTransition(() => {
-  //           reactionsRef.current = {
-  //             ...reactionsRef.current,
-  //             [data.payload]: (reactionsRef.current[data.payload] || 0) + 1,
-  //           };
-  //           setReactionsCount(reactionsRef.current);
-  //           localStorage.setItem(
-  //             'reactions',
-  //             JSON.stringify(reactionsRef.current)
-  //           );
-  //         });
-  //       } else {
-  //         // isUploading이 false일 때는 일반 처리
-  //         dispatch({ type: 'ADD', payload: data.payload });
-  //         reactionsRef.current = {
-  //           ...reactionsRef.current,
-  //           [data.payload]: (reactionsRef.current[data.payload] || 0) + 1,
-  //         };
-  //         setReactionsCount(reactionsRef.current);
-  //         localStorage.setItem(
-  //           'reactions',
-  //           JSON.stringify(reactionsRef.current)
-  //         );
-  //       }
-  //     } else if (data.type === 'question') {
-  //       setQuestions((prev) => [...prev, data.payload]);
-  //     } else if (data.type === 'request') {
-  //       setRequests((prev) => [...prev, data.payload]);
-  //     }
-  //   };
-
-  //   eventSource.onerror = () => {
-  //     eventSource.close();
-  //   };
-
-  //   return () => {
-  //     eventSource.close();
-  //   };
-  // }, [courseId]);
-
-  // 교수 질문 체크
-  const handleResolveClick = async (id: Question['id']) => {
-    const updatedQuestions = questions.filter((question) => question.id !== id);
-    await classroomRepository.checkQuestionByProfessor(id);
-
-    setQuestions(updatedQuestions);
-  };
+  useEffect(() => {
+    if (!sseRef.current) {
+      connectSSE();
+    }
 
-  //강의 종료
-  const handleCloseClass = () => {};
+    return () => {
+      sseRef.current?.close();
+      sseRef.current = null;
+    };
+  }, []);
 
   return (
     <>
       <div className={S.professorClassroom}>
-        {courseInfo && (
-          <PDFMainComponent
-            courseInfo={courseInfo}
-            setIsUploading={setIsUploading}
-            setModal={setModal}
-            courseId={Number(courseId)}
-            closeModal={closeModal}
-            reactionsCount={reactionsCount}
-            reactions={reactions}
-            dispatch={dispatch}
-            openModal={openModal}
-          />
-        )}
+        <PDFMainComponent
+          courseInfo={courseInfo}
+          setIsUploading={setIsUploading}
+          setModal={setModal}
+          closeModal={closeModal}
+          reactionsCount={reactionsCount}
+          reactions={reactions}
+          dispatch={dispatch}
+          openModal={openModal}
+          popupError={popupError}
+        />
         <PDFSideBar
           questions={questions}
           requests={requests}
diff --git a/front-end/src/pages/professor/course/classroom/components/PDFMainComponent.tsx b/front-end/src/pages/professor/course/classroom/components/PDFMainComponent.tsx
index 0bd50f7..64ca6ff 100644
--- a/front-end/src/pages/professor/course/classroom/components/PDFMainComponent.tsx
+++ b/front-end/src/pages/professor/course/classroom/components/PDFMainComponent.tsx
@@ -7,31 +7,31 @@ import ExpandSvg from '@/assets/icons/expansion.svg?react';
 import usePDF from '@/hooks/usePDF';
 import AccessCodeModal from './AccessCodeModal';
 import { Course, Reaction, ReactionType } from '@/core/model';
-import { professorRepository } from '@/di';
+import { courseRepository } from '@/di';
 import { Action } from '../ProfessorClassroom';
 
 type PDFMainComponentProps = {
-  courseInfo: Course;
+  courseInfo: Course | null;
   setIsUploading: React.Dispatch<React.SetStateAction<boolean>>;
   setModal: React.Dispatch<React.SetStateAction<ReactNode>>;
-  courseId: number;
   closeModal: () => void;
   openModal: () => void;
   reactions: ReactionType[];
   reactionsCount: Record<Reaction, number>;
   dispatch: React.Dispatch<Action>;
+  popupError: (error: unknown) => void;
 };
 
 const PDFMainComponent = ({
   courseInfo,
   setIsUploading,
   setModal,
-  courseId,
   closeModal,
   openModal,
   reactions,
   reactionsCount,
   dispatch,
+  popupError,
 }: PDFMainComponentProps) => {
   const {
     scale,
@@ -47,15 +47,24 @@ const PDFMainComponent = ({
 
   const fileInputRef = useRef<HTMLInputElement>(null);
 
-  // 처음 저장된 pdf 받아오기
   useEffect(() => {
     async function fetchPDF() {
-      const pdfUrl = await professorRepository.getProfessorPDF(courseId);
-      setPDF(pdfUrl);
-      loadPdf(pdfUrl);
+      try {
+        if (!courseInfo) {
+          return;
+        }
+        const pdfUrl = await courseRepository.getCourseFileUrl(courseInfo.id);
+        if (!pdfUrl) {
+          return;
+        }
+        setPDF(pdfUrl);
+        loadPdf(pdfUrl);
+      } catch (error) {
+        popupError(error);
+      }
     }
     fetchPDF();
-  }, [courseId, courseInfo]);
+  }, [courseInfo]);
 
   const handleCloseModal = () => {
     closeModal();
@@ -83,8 +92,8 @@ const PDFMainComponent = ({
         // 해당강의의 pdf가 변경되었다는것을 알려야함
         setIsUploading(false);
       } catch (error) {
-        //추후 에러 핸들링
-        console.log(error);
+        setIsUploading(false);
+        popupError(error);
       }
     }
   }
@@ -93,7 +102,7 @@ const PDFMainComponent = ({
     <div className={S.mainContainer}>
       <div className={S.mainHeader}>
         <div className={S.accessCodeContainer}>
-          <div className={S.accessCode}>입장코드 {courseInfo.accessCode}</div>
+          <div className={S.accessCode}>입장코드 {courseInfo?.accessCode}</div>
           <button
             className={S.expandCode}
             onClick={() =>
diff --git a/front-end/src/pages/professor/course/classroom/components/RequestBox.tsx b/front-end/src/pages/professor/course/classroom/components/RequestBox.tsx
index b0b63fc..66a019d 100644
--- a/front-end/src/pages/professor/course/classroom/components/RequestBox.tsx
+++ b/front-end/src/pages/professor/course/classroom/components/RequestBox.tsx
@@ -19,11 +19,11 @@ type RequestBoxProps = {
 };
 
 const EmojiType = {
-  hard: WishEmoji,
-  fast: WindEmoji,
-  question: BulbEmoji,
-  size: MagnifierEmoji,
-  sound: EarEmoji,
+  [RequestHard.kind]: WishEmoji,
+  [RequestFast.kind]: WindEmoji,
+  [RequestQuestion.kind]: BulbEmoji,
+  [RequestSize.kind]: MagnifierEmoji,
+  [RequestSound.kind]: EarEmoji,
 };
 
 const RequestBox = ({ request }: RequestBoxProps) => {
diff --git a/front-end/src/pages/professor/course/classroom/components/reaction/EmojiCounter.tsx b/front-end/src/pages/professor/course/classroom/components/reaction/EmojiCounter.tsx
index 61354ce..1b43f6c 100644
--- a/front-end/src/pages/professor/course/classroom/components/reaction/EmojiCounter.tsx
+++ b/front-end/src/pages/professor/course/classroom/components/reaction/EmojiCounter.tsx
@@ -19,12 +19,12 @@ type EmojiCounterProps = {
 };
 
 const CHIP_LIST = [
-  { type: 'okay', icon: OkayEmoji },
-  { type: 'clap', icon: ClapEmoji },
-  { type: 'thumb', icon: ThumbEmoji },
-  { type: 'scream', icon: ScreamEmoji },
-  { type: 'cry', icon: CryEmoji },
-  { type: 'like', icon: LikeEmoji },
+  { type: 'OKAY', icon: OkayEmoji },
+  { type: 'CLAP', icon: ClapEmoji },
+  { type: 'THUMBS_UP', icon: ThumbEmoji },
+  { type: 'SURPRISED', icon: ScreamEmoji },
+  { type: 'CRYING', icon: CryEmoji },
+  { type: 'HEART_EYES', icon: LikeEmoji },
 ] as const;
 
 const getEmojiIcon = (reaction: ReactionType) =>
diff --git a/front-end/src/repository/classroomRepository.ts b/front-end/src/repository/classroomRepository.ts
index b9bcea9..fa31e86 100644
--- a/front-end/src/repository/classroomRepository.ts
+++ b/front-end/src/repository/classroomRepository.ts
@@ -3,9 +3,12 @@ import { throwError } from './throwError';
 
 class ClassroomRepository {
   async startCourse(courseId: string): Promise<void> {
-    // API: POST /professors/courses/{courseId}/start
+    // API: PATCH /professors/courses/{courseId}/start
 
-    console.log('start course:', courseId);
+    const response = await fetch(`/api/professors/courses/${courseId}/start`, {
+      method: 'PATCH',
+    });
+    await throwError(response);
   }
 
   async enterCourse(accessCode: number): Promise<void> {
@@ -19,9 +22,12 @@ class ClassroomRepository {
   }
 
   async closeCourse(courseId: string): Promise<void> {
-    // API: POST /professors/courses/{courseId}/close
+    // API: PATCH /professors/courses/{courseId}/close
 
-    console.log('close course:', courseId);
+    const response = await fetch(`/api/professors/courses/${courseId}/close`, {
+      method: 'PATCH',
+    });
+    await throwError(response);
   }
 
   async checkQuestionByProfessor(questionId: string): Promise<void> {
@@ -36,8 +42,6 @@ class ClassroomRepository {
       }
     );
     await throwError(response);
-    const data = response.json();
-    return data;
   }
 
   async checkQuestionByStudent(questionId: string): Promise<void> {
diff --git a/front-end/src/repository/courseRepository.ts b/front-end/src/repository/courseRepository.ts
index 29df2dd..fbc7c27 100644
--- a/front-end/src/repository/courseRepository.ts
+++ b/front-end/src/repository/courseRepository.ts
@@ -57,7 +57,7 @@ type BackendCourse = {
   accessCode: string | number;
   fileName: string;
   questions: BackendQuestion[];
-  request: BackendRequests;
+  requests: BackendRequests;
 };
 
 class CourseRepository {
@@ -282,33 +282,28 @@ class CourseRepository {
       requests: [
         {
           type: RequestHard,
-          count:
-            data.request?.find((req) => req.type === RequestHard.kind)?.count ||
-            0,
+          count: data.requests?.find((req) => req.type === RequestHard.kind)
+            ?.count,
         },
         {
           type: RequestFast,
-          count:
-            data.request?.find((req) => req.type === RequestFast.kind)?.count ||
-            0,
+          count: data.requests?.find((req) => req.type === RequestFast.kind)
+            ?.count,
         },
         {
           type: RequestQuestion,
-          count:
-            data.request?.find((req) => req.type === RequestQuestion.kind)
-              ?.count || 0,
+          count: data.requests?.find((req) => req.type === RequestQuestion.kind)
+            ?.count,
         },
         {
           type: RequestSize,
-          count:
-            data.request?.find((req) => req.type === RequestSize.kind)?.count ||
-            0,
+          count: data.requests?.find((req) => req.type === RequestSize.kind)
+            ?.count,
         },
         {
           type: RequestSound,
-          count:
-            data.request?.find((req) => req.type === RequestSound.kind)
-              ?.count || 0,
+          count: data.requests?.find((req) => req.type === RequestSound.kind)
+            ?.count,
         },
       ],
     } as Course;
@@ -373,7 +368,7 @@ class CourseRepository {
 
     const body: Omit<
       BackendCourse,
-      'id' | 'accessCode' | 'fileName' | 'questions' | 'request'
+      'id' | 'accessCode' | 'fileName' | 'questions' | 'requests'
     > = {
       name: course.name,
       courseCode: course.code,
diff --git a/front-end/src/utils/courseAction.tsx b/front-end/src/utils/courseAction.tsx
index 538a8b5..ef382ca 100644
--- a/front-end/src/utils/courseAction.tsx
+++ b/front-end/src/utils/courseAction.tsx
@@ -4,7 +4,7 @@ import AlertModal from '../components/modal/AlertModal';
 import CourseModal from '../pages/professor/home/modal/CourseModal';
 import FileUploadPopupModal from '../components/modal/FileUploadPopupModal';
 import ClassStartModal from '../components/modal/ClassStartModal';
-import { courseRepository } from '@/di';
+import { classroomRepository, courseRepository } from '@/di';
 import ProfessorError from './professorError';
 import { NavigateFunction } from 'react-router';
 
@@ -123,7 +123,7 @@ const courseActions = ({
         course={course}
         handleClickBackButton={offModal}
         handleClickStartButton={() => {
-          console.log('Start course:', course.id);
+          classroomRepository.startCourse(course.id);
           offModal();
           navigate(`/professor/course/${course.id}/classroom`);
         }}