diff --git a/Main/src/main/java/com/kusitms29/backendH/api/sync/service/SyncDetailService.java b/Main/src/main/java/com/kusitms29/backendH/api/sync/service/SyncDetailService.java
index 5eb28b9..151751d 100644
--- a/Main/src/main/java/com/kusitms29/backendH/api/sync/service/SyncDetailService.java
+++ b/Main/src/main/java/com/kusitms29/backendH/api/sync/service/SyncDetailService.java
@@ -132,12 +132,13 @@ public List<SyncReviewResponseDto> getSyncReviewList(Long syncId, int take){
     public void joinSync(Long userId, Long syncId){
         Sync sync = syncReader.findById(syncId);
         User owner = userReader.getByUserId(sync.getUser().getId());
+        User joinUser = userReader.getByUserId(userId);
         Participation newParticipation =Participation.createParticipation(User.from(userId), Sync.from(syncId));
         participationAppender.saveParticipation(newParticipation);
         int count = participationManager.countParticipationBySyncId(syncId);
         Boolean isPossible = syncManager.validateCreateRoom(sync,count);
         List<User> userList = participationReader.findAllBySyncId(syncId).stream().map(participation -> userReader.getByUserId(participation.getUser().getId())).toList();
-        roomAppender.createRoom(userList,isPossible,syncId,owner);
+        roomAppender.createRoom(userList,isPossible,syncId,owner,joinUser);
     }
     public Boolean bookmark(Long userId, SyncBookmarkRequestDto syncBookmarkRequestDto){
         if(syncBookmarkRequestDto.isMarked()){
diff --git a/Main/src/main/java/com/kusitms29/backendH/domain/chat/service/RoomAppender.java b/Main/src/main/java/com/kusitms29/backendH/domain/chat/service/RoomAppender.java
index 09810c9..3d3bafd 100644
--- a/Main/src/main/java/com/kusitms29/backendH/domain/chat/service/RoomAppender.java
+++ b/Main/src/main/java/com/kusitms29/backendH/domain/chat/service/RoomAppender.java
@@ -22,13 +22,13 @@ public class RoomAppender {
     private final RoomRepository roomRepository;
     private final PushNotificationService pushNotificationService;
     private final SyncReader syncReader;
+    private final RoomReader roomReader;
     @Transactional
-    public void createRoom(List<User> userList, Boolean isPossible, Long syncId, User owner) {
+    public void createRoom(List<User> userList, Boolean isPossible, Long syncId, User owner,User joinUser) {
         Room room = null;
-
+        Sync sync = syncReader.findById(syncId);
         if (isPossible) {
             // 채팅 내용 추가
-            Sync sync = syncReader.findById(syncId);
 
             List<ChatContent> contents = new ArrayList<>();
 
@@ -45,22 +45,14 @@ public void createRoom(List<User> userList, Boolean isPossible, Long syncId, Use
             );
             for (User user : userList) {
                 if (sync.getUser().getId().equals(user.getId())) {
-                    ChatContent chatContent = ChatContent.createChatContent(user.getUserName(), "환영합니다", room,"https://sync-content-bucket-01.s3.ap-northeast-2.amazonaws.com/94f1a566-0072-45e9-944f-707a6e21bbbf.png");
+                    ChatContent chatContent = ChatContent.createChatContent(user.getUserName(), "모두 반가워요~", room,"https://sync-content-bucket-01.s3.ap-northeast-2.amazonaws.com/a2d3a182-9054-42b9-b439-616bcbba9e87.png");
                     contents.add(chatContent);
                 }
             }
             roomRepository.save(room);
         } else {
-            List<ChatUser> chatUsers = userList.stream()
-                    .map(ChatUser::createChatUser)
-                    .toList();
-
-            // 기존 채팅방에 사용자 추가
-            for (ChatUser chatUser : chatUsers) {
-                if (!room.getChatUserList().contains(chatUser)) {
-                    room.addChatRoom(chatUser);
-                }
-            }
+            room = roomReader.getRoomBySyncName(sync.getSyncName());
+            room.addChatRoom(ChatUser.createChatUser(joinUser));
             roomRepository.save(room);
         }
         // 채팅방 개설 알림
diff --git a/Main/src/main/java/com/kusitms29/backendH/domain/chat/service/RoomReader.java b/Main/src/main/java/com/kusitms29/backendH/domain/chat/service/RoomReader.java
new file mode 100644
index 0000000..8ebbcd8
--- /dev/null
+++ b/Main/src/main/java/com/kusitms29/backendH/domain/chat/service/RoomReader.java
@@ -0,0 +1,19 @@
+package com.kusitms29.backendH.domain.chat.service;
+
+import com.kusitms29.backendH.domain.chat.entity.Room;
+import lombok.RequiredArgsConstructor;
+import org.springframework.data.mongodb.core.MongoTemplate;
+import org.springframework.data.mongodb.core.query.Criteria;
+import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.stereotype.Service;
+
+@Service
+@RequiredArgsConstructor
+public class RoomReader {
+    private final MongoTemplate mongoTemplate;
+    public Room getRoomBySyncName(String syncName){
+        Query query = new Query();
+        query.addCriteria(Criteria.where("syncName").is(syncName));
+        return mongoTemplate.findOne(query, Room.class);
+    }
+}
diff --git a/Main/src/main/java/com/kusitms29/backendH/global/common/HealthCheckApiController.java b/Main/src/main/java/com/kusitms29/backendH/global/common/HealthCheckApiController.java
index 15b5c8a..fadec09 100644
--- a/Main/src/main/java/com/kusitms29/backendH/global/common/HealthCheckApiController.java
+++ b/Main/src/main/java/com/kusitms29/backendH/global/common/HealthCheckApiController.java
@@ -52,10 +52,11 @@ public class HealthCheckApiController {
     private String KAKAO_REDIRECT_URI;
     private Properties promptMap = new Properties();
     private final TranslateConfig translateConfig;
-    public HealthCheckApiController(MongoTemplate mongoTemplate, RoomRepository roomRepository, TranslateConfig translateConfig) {
+    public HealthCheckApiController(UserReader userReader, MongoTemplate mongoTemplate, RoomRepository roomRepository, TranslateConfig translateConfig) {
         this.mongoTemplate = mongoTemplate;
         this.roomRepository = roomRepository;
         this.translateConfig = translateConfig;
+        this.userReader = userReader;
     }
     @GetMapping("google")
     public ResponseEntity<String> googleOauth(HttpServletRequest request) throws IOException {