diff --git a/src/main/java/com/ikdaman/domain/mybook/service/MyBookServiceImpl.java b/src/main/java/com/ikdaman/domain/mybook/service/MyBookServiceImpl.java
index 95629d3..f190eee 100644
--- a/src/main/java/com/ikdaman/domain/mybook/service/MyBookServiceImpl.java
+++ b/src/main/java/com/ikdaman/domain/mybook/service/MyBookServiceImpl.java
@@ -80,6 +80,11 @@ public MyBookRes addMyBook(UUID memberId, MyBookReq dto) {
                     .build());
         }
 
+        // 한 사용자가 책장에 같은 책을 중복으로 저장할 수 없음
+        if(myBookRepository.existsMyBookByMemberIdAndBook(memberId, book)) {
+            throw new BaseException(MY_BOOK_ALREADY_EXISTS);
+        }
+
         MyBook myBook = MyBook.builder()
                 .memberId(memberId)
                 .book(book)
diff --git a/src/main/java/com/ikdaman/global/exception/ErrorCode.java b/src/main/java/com/ikdaman/global/exception/ErrorCode.java
index 1fbfead..c1d574b 100644
--- a/src/main/java/com/ikdaman/global/exception/ErrorCode.java
+++ b/src/main/java/com/ikdaman/global/exception/ErrorCode.java
@@ -75,7 +75,7 @@ public enum ErrorCode {
     CONFLICT_NICKNAME(HttpStatus.CONFLICT.value(), 4090201, "사용중인 닉네임입니다."),
     // MyBook(03)
     NOT_FOUND_MY_BOOK(HttpStatus.NOT_FOUND.value(), 4040301,"해당 MyBook을 찾을 수 없습니다."),
-    MY_BOOK_ALREADY_EXISTS(HttpStatus.CONFLICT.value(), 4090302, "이미 책장에 추가된 책입니다."),
+    MY_BOOK_ALREADY_EXISTS(HttpStatus.CONFLICT.value(), 4090302, "이미 가지고 있는 책이에요!"),
 
     // Notice(04)