diff --git a/src/sora.cpp b/src/sora.cpp
index d14ca65..8f5518b 100644
--- a/src/sora.cpp
+++ b/src/sora.cpp
@@ -541,11 +541,10 @@ void Sora::Disconnect() {
 
 void Sora::SwitchCamera(const sora_conf::internal::CameraConfig& cc) {
   RTC_LOG(LS_INFO) << "SwitchCamera: " << jsonif::to_json(cc);
-  boost::asio::post(*ioc_, [self = shared_from_this(), cc = cc]() {
-    self->DoSwitchCamera(cc);
-  });
-}
-void Sora::DoSwitchCamera(const sora_conf::internal::CameraConfig& cc) {
+
+  // このあたりのキャプチャラ作成は、IO スレッドではなく Unity スレッドで行う。
+  // （DoConnect で作成したキャプチャラは Unity スレッド上で実行されてるので、
+  //   全て同じスレッドでやる必要がある）
   std::function<void(const webrtc::VideoFrame& frame)> on_frame;
   if (on_capturer_frame_) {
     on_frame = [on_frame =
@@ -582,10 +581,40 @@ void Sora::DoSwitchCamera(const sora_conf::internal::CameraConfig& cc) {
 
   std::string video_track_id = rtc::CreateRandomString(16);
   auto video_track = factory_->CreateVideoTrack(video_track_id, capturer.get());
-  renderer_->ReplaceTrack(video_track_.get(), video_track.get());
-  video_sender_->SetTrack(video_track.get());
+
+  // video_track_ をこのスレッド(Unity スレッド)で設定したいので、
+  // IO スレッドの実行完了を待つ
+  std::promise<void> p;
+  std::future<void> f = p.get_future();
+  boost::asio::post(*ioc_,
+                    [self = shared_from_this(), cc = cc, video_track, &p]() {
+                      self->DoSwitchCamera(cc, video_track);
+                      p.set_value();
+                    });
+  f.wait();
+
   video_track_ = video_track;
 }
+void Sora::DoSwitchCamera(
+    const sora_conf::internal::CameraConfig& cc,
+    rtc::scoped_refptr<webrtc::VideoTrackInterface> video_track) {
+  if (video_track_ == nullptr) {
+    webrtc::RTCErrorOr<rtc::scoped_refptr<webrtc::RtpSenderInterface>>
+        video_result = signaling_->GetPeerConnection()->AddTrack(video_track,
+                                                                 {stream_id_});
+    video_sender_ = video_result.value();
+
+    auto track_id = renderer_->AddTrack(video_track.get());
+    PushEvent([this, track_id]() {
+      if (on_add_track_) {
+        on_add_track_(track_id, "");
+      }
+    });
+  } else {
+    renderer_->ReplaceTrack(video_track_.get(), video_track.get());
+  }
+  video_sender_->SetTrack(video_track.get());
+}
 
 void Sora::RenderCallbackStatic(int event_id) {
   auto sora = (Sora*)IdPointer::Instance().Lookup(event_id);
@@ -838,16 +867,16 @@ void Sora::OnSetOffer(std::string offer) {
       on_set_offer_(offer);
     }
   });
-  std::string stream_id = rtc::CreateRandomString(16);
+  stream_id_ = rtc::CreateRandomString(16);
   if (audio_track_ != nullptr) {
     webrtc::RTCErrorOr<rtc::scoped_refptr<webrtc::RtpSenderInterface>>
         audio_result = signaling_->GetPeerConnection()->AddTrack(audio_track_,
-                                                                 {stream_id});
+                                                                 {stream_id_});
   }
   if (video_track_ != nullptr) {
     webrtc::RTCErrorOr<rtc::scoped_refptr<webrtc::RtpSenderInterface>>
         video_result = signaling_->GetPeerConnection()->AddTrack(video_track_,
-                                                                 {stream_id});
+                                                                 {stream_id_});
     video_sender_ = video_result.value();
   }
 
diff --git a/src/sora.h b/src/sora.h
index 3b6d485..7a72db8 100644
--- a/src/sora.h
+++ b/src/sora.h
@@ -92,7 +92,9 @@ class Sora : public std::enable_shared_from_this<Sora>,
  private:
   void DoConnect(const sora_conf::internal::ConnectConfig& config,
                  std::function<void(int, std::string)> on_disconnect);
-  void DoSwitchCamera(const sora_conf::internal::CameraConfig& cc);
+  void DoSwitchCamera(
+      const sora_conf::internal::CameraConfig& cc,
+      rtc::scoped_refptr<webrtc::VideoTrackInterface> video_track);
 
   static rtc::scoped_refptr<UnityAudioDevice> CreateADM(
       webrtc::TaskQueueFactory* task_queue_factory,
@@ -168,6 +170,8 @@ class Sora : public std::enable_shared_from_this<Sora>,
 
   std::map<ptrid_t, std::string> connection_ids_;
 
+  std::string stream_id_;
+
   rtc::scoped_refptr<webrtc::VideoTrackSourceInterface> capturer_;
   int capturer_type_ = 0;
   std::shared_ptr<CapturerSink> capturer_sink_;