diff --git a/apps/client/src/hooks/useAppFlow.ts b/apps/client/src/hooks/useAppFlow.ts
index c6ffc5d..d4359fc 100644
--- a/apps/client/src/hooks/useAppFlow.ts
+++ b/apps/client/src/hooks/useAppFlow.ts
@@ -35,7 +35,8 @@
 
 type JoinFailureReason =
   | domain.room.JoinRoomRejectedPayload["reason"]
-  | "timeout";
+  | "timeout"
+  | "playing";
 
 type JoinFailure = {
   reason: JoinFailureReason;
@@ -119,6 +120,10 @@
         return `ルーム ${joinFailure.roomId ?? ""} は満員です`;
       }
 
+      if (joinFailure.reason === "playing") {
+        return `ルーム ${joinFailure.roomId ?? ""} はゲーム中のため参加できません`;
+      }
+
       if (joinFailure.reason === "duplicate") {
         return `ルーム ${joinFailure.roomId ?? ""} への参加要求が重複しました`;
       }
diff --git a/apps/server/src/application/coordinators/coordinatorDeps.ts b/apps/server/src/application/coordinators/coordinatorDeps.ts
index d222a64..11cede5 100644
--- a/apps/server/src/application/coordinators/coordinatorDeps.ts
+++ b/apps/server/src/application/coordinators/coordinatorDeps.ts
@@ -4,6 +4,7 @@
  */
 import type {
   CleanupGameRuntimePort,
+  DeleteRoomPort,
   DisconnectRoomPort,
   FindGameByRoomPort,
   FindRoomByIdPort,
@@ -14,8 +15,8 @@
 
 /** START_GAME調停で利用する依存集合 */
 export type StartGameCoordinatorDeps = {
-  roomManager: FindRoomByOwnerPort & RoomPhaseTransitionPort;
-  runtimeRegistry: FindGameByRoomPort;
+  roomManager: FindRoomByOwnerPort & RoomPhaseTransitionPort & DeleteRoomPort;
+  runtimeRegistry: FindGameByRoomPort & CleanupGameRuntimePort;
 };
 
 /** READY_FOR_GAME調停で利用する依存集合 */
diff --git a/apps/server/src/application/coordinators/startGameCoordinator.ts b/apps/server/src/application/coordinators/startGameCoordinator.ts
index dc67565..72407a7 100644
--- a/apps/server/src/application/coordinators/startGameCoordinator.ts
+++ b/apps/server/src/application/coordinators/startGameCoordinator.ts
@@ -106,7 +106,8 @@
     gameSession: gameManager,
     bombStore: gameManager,
     onGameEnd: () => {
-      roomManager.markRoomWaiting(updatedRoom.roomId);
+      roomManager.deleteRoom(updatedRoom.roomId);
+      runtimeRegistry.cleanupGameManagerForRoom(updatedRoom.roomId);
     },
     output,
   });
diff --git a/apps/server/src/domains/room/RoomManager.ts b/apps/server/src/domains/room/RoomManager.ts
index 6a7be2e..67b532c 100644
--- a/apps/server/src/domains/room/RoomManager.ts
+++ b/apps/server/src/domains/room/RoomManager.ts
@@ -62,4 +62,9 @@
   public markRoomWaiting(roomId: string): RoomPhaseTransitionResult {
     return this.roomPhaseService.markRoomWaiting(roomId);
   }
+
+  // ルームを削除する
+  public deleteRoom(roomId: string): boolean {
+    return this.rooms.delete(roomId);
+  }
 }
\ No newline at end of file
diff --git a/apps/server/src/domains/room/application/ports/roomUseCasePorts.ts b/apps/server/src/domains/room/application/ports/roomUseCasePorts.ts
index 8826220..e0cbd1e 100644
--- a/apps/server/src/domains/room/application/ports/roomUseCasePorts.ts
+++ b/apps/server/src/domains/room/application/ports/roomUseCasePorts.ts
@@ -26,7 +26,7 @@
 /** ルーム参加処理の実行結果 */
 export type JoinRoomResult = {
   room: domain.room.Room;
-  status: "joined" | "duplicate" | "full";
+  status: "joined" | "duplicate" | "full" | "playing";
 };
 
 /** ルームユースケースが利用する出力ポート */
@@ -78,6 +78,11 @@
   getRoomById(roomId: string): domain.room.Room | undefined;
 }
 
+/** ゲーム終了時にルームを削除する操作ポート */
+export interface DeleteRoomPort {
+  deleteRoom(roomId: string): boolean;
+}
+
 /** ルーム参加後にゲームランタイムを確保する操作ポート */
 export interface EnsureGameRuntimePort {
   ensureGameManagerForRoom(roomId: string): void;
diff --git a/apps/server/src/domains/room/application/services/RoomJoinService.ts b/apps/server/src/domains/room/application/services/RoomJoinService.ts
index 8b72619..979b5b2 100644
--- a/apps/server/src/domains/room/application/services/RoomJoinService.ts
+++ b/apps/server/src/domains/room/application/services/RoomJoinService.ts
@@ -32,6 +32,17 @@
       });
     }
 
+    // 待機中以外のルームへの参加を拒否する
+    if (room.status !== domain.room.RoomPhase.WAITING) {
+      logEvent(logScopes.ROOM_JOIN_SERVICE, {
+        event: roomDomainLogEvents.PLAYER_JOIN,
+        result: logResults.REJECTED_ROOM_PLAYING,
+        roomId,
+        socketId,
+      });
+      return { room, status: "playing" };
+    }
+
     // 同一ソケットの重複参加を防止する
     const alreadyJoined = room.players.some((player) => player.id === socketId);
     if (alreadyJoined) {
diff --git a/apps/server/src/logging/constants/results.ts b/apps/server/src/logging/constants/results.ts
index f5ff65f..6ab8c75 100644
--- a/apps/server/src/logging/constants/results.ts
+++ b/apps/server/src/logging/constants/results.ts
@@ -28,6 +28,7 @@
   REJECTED: "rejected",
   REJECTED_DUPLICATE: "rejected_duplicate",
   REJECTED_ROOM_FULL: "rejected_room_full",
+  REJECTED_ROOM_PLAYING: "rejected_room_playing",
   REMOVED: "removed",
   SESSION_DISPOSED_EMPTY_ROOM: "session_disposed_empty_room",
   STARTED: "started",
diff --git a/apps/server/src/logging/contracts/payloadByScope.ts b/apps/server/src/logging/contracts/payloadByScope.ts
index 8620418..044d3d0 100644
--- a/apps/server/src/logging/contracts/payloadByScope.ts
+++ b/apps/server/src/logging/contracts/payloadByScope.ts
@@ -27,6 +27,7 @@
   result:
     | typeof logResults.REJECTED_ROOM_FULL
     | typeof logResults.REJECTED_DUPLICATE
+    | typeof logResults.REJECTED_ROOM_PLAYING
     | typeof logResults.IGNORED_INVALID_PAYLOAD
     | typeof logResults.IGNORED_MISSING_ROOM;
   socketId: string;
@@ -224,6 +225,7 @@
   result:
     | typeof logResults.IGNORED_DUPLICATE
     | typeof logResults.IGNORED_ROOM_FULL
+    | typeof logResults.REJECTED_ROOM_PLAYING
     | typeof logResults.JOINED;
   roomId: string;
   socketId: string;
diff --git a/apps/server/src/network/handlers/room/roomEventOrchestrators.ts b/apps/server/src/network/handlers/room/roomEventOrchestrators.ts
index b3b4996..4fbd750 100644
--- a/apps/server/src/network/handlers/room/roomEventOrchestrators.ts
+++ b/apps/server/src/network/handlers/room/roomEventOrchestrators.ts
@@ -49,6 +49,15 @@
       });
       return;
 
+    case "playing":
+      logEvent(logScopes.NETWORK, {
+        event: roomUseCaseLogEvents.JOIN_ROOM,
+        result: logResults.REJECTED_ROOM_PLAYING,
+        roomId: payload.roomId,
+        socketId: deps.socketId,
+      });
+      return;
+
     case "duplicate":
       logEvent(logScopes.NETWORK, {
         event: roomUseCaseLogEvents.JOIN_ROOM,
diff --git a/packages/shared/src/domains/room/room.type.ts b/packages/shared/src/domains/room/room.type.ts
index ce8c529..6fad7d7 100644
--- a/packages/shared/src/domains/room/room.type.ts
+++ b/packages/shared/src/domains/room/room.type.ts
@@ -31,7 +31,7 @@
 }
 
 /** ルーム参加拒否理由 */
-export type JoinRoomRejectedReason = "full" | "duplicate";
+export type JoinRoomRejectedReason = "full" | "duplicate" | "playing";
 
 /** ルーム参加拒否通知ペイロード */
 export interface JoinRoomRejectedPayload {
diff --git a/test/load-bot.constants.ts b/test/load-bot.constants.ts
index 48a406f..b8e9ad8 100644
--- a/test/load-bot.constants.ts
+++ b/test/load-bot.constants.ts
@@ -6,7 +6,7 @@
 
 export const URL = NETWORK_CONFIG.PROD_SERVER_URL;
 export const DEV_URL = NETWORK_CONFIG.DEV_SERVER_URL;
-export const BOTS = 10;
+export const BOTS = 99;
 export const DURATION_MS = Infinity;
 export const JOIN_DELAY_MS = 25;
 export const MOVE_TICK_MS = GAME_CONFIG.PLAYER_POSITION_UPDATE_MS;
@@ -19,7 +19,7 @@
 export const MAX_Y = GAME_CONFIG.GRID_ROWS;
 export const BOT_CAN_MOVE = true;
 export const BOT_CAN_PLACE_BOMB = true;
-export const ROOM_ID = "12";
+export const ROOM_ID = "1";
 export const START_GAME = true;
 export const SOCKET_PATH = NETWORK_CONFIG.SOCKET_IO_PATH;
 export const SOCKET_TRANSPORTS = [...NETWORK_CONFIG.SOCKET_TRANSPORTS];