diff --git a/apps/server/src/application/coordinators/startGameCoordinator.ts b/apps/server/src/application/coordinators/startGameCoordinator.ts
index efb030c..602e37b 100644
--- a/apps/server/src/application/coordinators/startGameCoordinator.ts
+++ b/apps/server/src/application/coordinators/startGameCoordinator.ts
@@ -16,6 +16,7 @@
   ownerId: string;
   gameManager: StartGamePort;
   roomManager: StartGameRoomPort;
+  onRoomGameEnded?: (roomId: string) => void;
   output: Pick<
     GameOutputPort,
     | "publishUpdatePlayersToRoom"
@@ -31,6 +32,7 @@
   ownerId,
   gameManager,
   roomManager,
+  onRoomGameEnded,
   output,
 }: StartGameCoordinatorParams) => {
   const room = roomManager.getRoomByOwnerId(ownerId);
@@ -80,6 +82,7 @@
     gameManager,
     onGameEnd: () => {
       roomManager.markRoomWaiting(updatedRoom.roomId);
+      onRoomGameEnded?.(updatedRoom.roomId);
     },
     output,
   });
diff --git a/apps/server/src/domains/room/application/ports/roomUseCasePorts.ts b/apps/server/src/domains/room/application/ports/roomUseCasePorts.ts
index c0e5a7b..9845676 100644
--- a/apps/server/src/domains/room/application/ports/roomUseCasePorts.ts
+++ b/apps/server/src/domains/room/application/ports/roomUseCasePorts.ts
@@ -30,3 +30,8 @@
 export interface FindRoomByPlayerPort {
   getRoomByPlayerId(playerId: string): roomTypes.Room | undefined;
 }
+
+/** ルームIDでの存在確認に利用する参照ポート */
+export interface FindRoomByIdPort {
+  getRoomById(roomId: string): roomTypes.Room | undefined;
+}
diff --git a/apps/server/src/network/handlers/GameHandler.ts b/apps/server/src/network/handlers/GameHandler.ts
index f317903..139735f 100644
--- a/apps/server/src/network/handlers/GameHandler.ts
+++ b/apps/server/src/network/handlers/GameHandler.ts
@@ -5,3 +5,6 @@
  */
 /** ゲームイベント受信ハンドラ登録関数を外部参照向けに再公開 */
 export { registerGameHandlers } from "./game/registerGameHandlers";
+
+/** ルーム終了時の爆弾状態掃除関数を外部参照向けに再公開 */
+export { clearBombRoomState } from "./game/registerGameHandlers";
diff --git a/apps/server/src/network/handlers/game/registerGameHandlers.ts b/apps/server/src/network/handlers/game/registerGameHandlers.ts
index 679430a..379f0d6 100644
--- a/apps/server/src/network/handlers/game/registerGameHandlers.ts
+++ b/apps/server/src/network/handlers/game/registerGameHandlers.ts
@@ -22,6 +22,7 @@
 import { createGameOutputAdapter } from "./createGameOutputAdapter";
 const roomBombDedupTable = new Map<string, Map<string, number>>();
 const roomBombSerialTable = new Map<string, number>();
+const isBombRoomStateDebugEnabled = process.env.NODE_ENV !== "production";
 
 const cleanupExpiredBombDedup = (roomId: string, nowMs: number) => {
   const roomTable = roomBombDedupTable.get(roomId);
@@ -58,6 +59,20 @@
   return `${roomId}:${serial}`;
 };
 
+/** 指定ルームの爆弾採番状態と重複排除状態を破棄する */
+export const clearBombRoomState = (roomId: string, reason: "game-ended" | "room-deleted"): void => {
+  const hadDedupState = roomBombDedupTable.delete(roomId);
+  const hadSerialState = roomBombSerialTable.delete(roomId);
+
+  if (!isBombRoomStateDebugEnabled) {
+    return;
+  }
+
+  console.debug(
+    `[BombState] cleared room=${roomId} reason=${reason} dedup=${hadDedupState} serial=${hadSerialState}`
+  );
+};
+
 /** ゲーム受信イベントごとの入力検証関数を保持するテーブル */
 const gamePayloadValidators = {
   [protocol.SocketEvents.PING]: isPingPayload,
@@ -107,6 +122,9 @@
       ownerId: socket.id,
       gameManager,
       roomManager,
+      onRoomGameEnded: (roomId) => {
+        clearBombRoomState(roomId, "game-ended");
+      },
       output: gameOutputAdapter,
     });
   });
diff --git a/apps/server/src/network/handlers/registerConnectionHandlers.ts b/apps/server/src/network/handlers/registerConnectionHandlers.ts
index 66850a8..555dc51 100644
--- a/apps/server/src/network/handlers/registerConnectionHandlers.ts
+++ b/apps/server/src/network/handlers/registerConnectionHandlers.ts
@@ -7,7 +7,7 @@
 import { disconnectCoordinator } from "@server/application/coordinators/disconnectCoordinator";
 import { logEvent } from "@server/logging/logger";
 import { logResults, logScopes } from "@server/logging/index";
-import { registerGameHandlers } from "./GameHandler";
+import { clearBombRoomState, registerGameHandlers } from "./GameHandler";
 import { registerRoomHandlers } from "./RoomHandler";
 import { createGameDisconnectOutputAdapter } from "./game/createGameOutputAdapter";
 import { createRoomDisconnectOutputAdapter } from "./room/createRoomOutputAdapter";
@@ -36,6 +36,8 @@
     registerGameHandlers(io, socket, gameManager, roomManager);
 
     socket.on(protocol.SocketEvents.DISCONNECT, () => {
+      const roomIdBeforeDisconnect = roomManager.getRoomByPlayerId(socket.id)?.roomId;
+
       // 切断ログ記録後にドメイン別の後処理を実行する
       logEvent(logScopes.NETWORK, {
         event: protocol.SocketEvents.DISCONNECT,
@@ -50,6 +52,10 @@
         gameOutput: gameDisconnectOutputAdapter,
         roomOutput: roomDisconnectOutputAdapter,
       });
+
+      if (roomIdBeforeDisconnect && !roomManager.getRoomById(roomIdBeforeDisconnect)) {
+        clearBombRoomState(roomIdBeforeDisconnect, "room-deleted");
+      }
     });
   });
 };
diff --git a/apps/server/src/network/types/connectionPorts.ts b/apps/server/src/network/types/connectionPorts.ts
index dcb61a3..bd7a12a 100644
--- a/apps/server/src/network/types/connectionPorts.ts
+++ b/apps/server/src/network/types/connectionPorts.ts
@@ -13,6 +13,7 @@
 } from "@server/domains/game/application/ports/gameUseCasePorts";
 import type {
   DisconnectRoomPort,
+  FindRoomByIdPort,
   FindRoomByPlayerPort,
   JoinRoomPort,
 } from "@server/domains/room/application/ports/roomUseCasePorts";
@@ -39,6 +40,7 @@
 export type SocketConnectionRoomPort =
   & ConnectionRoomPort
   & DisconnectRoomPort
+  & FindRoomByIdPort
   & FindRoomByPlayerPort;
 
 /** ソケット接続ハンドラで受け取るマネージャ依存の束 */