diff --git a/apps/client/src/scenes/game/GameManager.ts b/apps/client/src/scenes/game/GameManager.ts
index 3eaa308..c56cc12 100644
--- a/apps/client/src/scenes/game/GameManager.ts
+++ b/apps/client/src/scenes/game/GameManager.ts
@@ -101,7 +101,7 @@
       gameMap: this.gameMap,
       onGameStart: this.setGameStart.bind(this),
       onGameEnd: this.lockInput.bind(this),
-      onBombPlaced: (payload) => {
+      onBombPlacedFromNetwork: (payload) => {
         const bombId = createBombIdFromPayload(payload);
         this.upsertBombFromNetwork(bombId, payload);
       },
diff --git a/apps/client/src/scenes/game/application/GameNetworkSync.ts b/apps/client/src/scenes/game/application/GameNetworkSync.ts
index 8cb19a4..783e3ca 100644
--- a/apps/client/src/scenes/game/application/GameNetworkSync.ts
+++ b/apps/client/src/scenes/game/application/GameNetworkSync.ts
@@ -5,7 +5,7 @@
  */
 import { Container } from "pixi.js";
 import type {
-  BombPlacedPayload,
+  BombNetworkPayload,
   CurrentPlayersPayload,
   GameStartPayload,
   NewPlayerPayload,
@@ -27,7 +27,7 @@
   gameMap: GameMapController;
   onGameStart: (startTime: number) => void;
   onGameEnd: () => void;
-  onBombPlaced: (payload: BombPlacedPayload) => void;
+  onBombPlacedFromNetwork: (payload: BombNetworkPayload) => void;
 };
 
 /** ゲーム中のネットワークイベント購読と同期処理を管理する */
@@ -38,7 +38,7 @@
   private gameMap: GameMapController;
   private onGameStart: (startTime: number) => void;
   private onGameEnd: () => void;
-  private onBombPlaced: (payload: BombPlacedPayload) => void;
+  private onBombPlacedFromNetwork: (payload: BombNetworkPayload) => void;
   private isBound = false;
 
   private debugLog = (message: string) => {
@@ -99,18 +99,26 @@
     this.onGameEnd();
   };
 
-  private handleBombPlaced = (payload: BombPlacedPayload) => {
-    this.onBombPlaced(payload);
+  private handleBombPlaced = (payload: BombNetworkPayload) => {
+    this.onBombPlacedFromNetwork(payload);
   };
 
-  constructor({ worldContainer, players, myId, gameMap, onGameStart, onGameEnd, onBombPlaced }: GameNetworkSyncOptions) {
+  constructor({
+    worldContainer,
+    players,
+    myId,
+    gameMap,
+    onGameStart,
+    onGameEnd,
+    onBombPlacedFromNetwork,
+  }: GameNetworkSyncOptions) {
     this.worldContainer = worldContainer;
     this.players = players;
     this.myId = myId;
     this.gameMap = gameMap;
     this.onGameStart = onGameStart;
     this.onGameEnd = onGameEnd;
-    this.onBombPlaced = onBombPlaced;
+    this.onBombPlacedFromNetwork = onBombPlacedFromNetwork;
   }
 
   public bind() {
diff --git a/apps/server/src/network/handlers/game/registerGameHandlers.ts b/apps/server/src/network/handlers/game/registerGameHandlers.ts
index 97052ea..bc551d4 100644
--- a/apps/server/src/network/handlers/game/registerGameHandlers.ts
+++ b/apps/server/src/network/handlers/game/registerGameHandlers.ts
@@ -3,7 +3,7 @@
  * ゲーム関連イベントの受信ハンドラを登録する
  */
 import { Server, Socket } from "socket.io";
-import { protocol } from "@repo/shared";
+import { config, createBombIdFromPayload, protocol } from "@repo/shared";
 import { readyForGameCoordinator } from "@server/application/coordinators/readyForGameCoordinator";
 import { startGameCoordinator } from "@server/application/coordinators/startGameCoordinator";
 import type {
@@ -20,6 +20,36 @@
 import { createServerSocketOnBridge } from "@server/network/handlers/socketEventBridge";
 import { createPayloadGuard } from "@server/network/handlers/payloadGuard";
 import { createGameOutputAdapter } from "./createGameOutputAdapter";
+const roomBombDedupTable = new Map<string, Map<string, number>>();
+
+const cleanupExpiredBombDedup = (roomId: string, nowMs: number) => {
+  const roomTable = roomBombDedupTable.get(roomId);
+  if (!roomTable) return;
+
+  roomTable.forEach((expiresAtMs, bombId) => {
+    if (expiresAtMs <= nowMs) {
+      roomTable.delete(bombId);
+    }
+  });
+
+  if (roomTable.size === 0) {
+    roomBombDedupTable.delete(roomId);
+  }
+};
+
+const shouldBroadcastBombPlaced = (roomId: string, bombId: string, nowMs: number) => {
+  cleanupExpiredBombDedup(roomId, nowMs);
+
+  const roomTable = roomBombDedupTable.get(roomId) ?? new Map<string, number>();
+  if (roomTable.has(bombId)) {
+    return false;
+  }
+
+  const ttlMs = config.GAME_CONFIG.BOMB_FUSE_MS + config.GAME_CONFIG.BOMB_DEDUP_EXTRA_TTL_MS;
+  roomTable.set(bombId, nowMs + ttlMs);
+  roomBombDedupTable.set(roomId, roomTable);
+  return true;
+};
 
 /** 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 = {
@@ -108,6 +138,12 @@
       return;
     }
 
+    const nowMs = Date.now();
+    const bombId = createBombIdFromPayload(data);
+    if (!shouldBroadcastBombPlaced(roomId, bombId, nowMs)) {
+      return;
+    }
+
     common.emitToRoom(roomId, protocol.SocketEvents.BOMB_PLACED, data);
   });
 };
diff --git a/packages/shared/src/config/README.md b/packages/shared/src/config/README.md
index bce6cce..027f1af 100644
--- a/packages/shared/src/config/README.md
+++ b/packages/shared/src/config/README.md
@@ -24,6 +24,7 @@
 - `GAME_CONFIG.BOMB_RADIUS_GRID`: 爆風半径（グリッド単位）
 - `GAME_CONFIG.BOMB_FUSE_MS`: 爆弾設置から爆発までの時間（ms）
 - `GAME_CONFIG.BOMB_COOLDOWN_MS`: 次の爆弾を置けるまでの待機時間（ms）
+- `GAME_CONFIG.BOMB_DEDUP_EXTRA_TTL_MS`: サーバー側の爆弾重複排除で保持時間に加算する猶予（ms）
 - `GAME_CONFIG.TEAM_COUNT`: チーム総数
 - `TEAM_NAMES`: `teamId` 順の表示名配列
 - `validateTeamConfig`: チーム関連設定（件数整合性）を検証する関数
diff --git a/packages/shared/src/config/gameConfig.ts b/packages/shared/src/config/gameConfig.ts
index 07bfc27..f81bf92 100644
--- a/packages/shared/src/config/gameConfig.ts
+++ b/packages/shared/src/config/gameConfig.ts
@@ -23,6 +23,7 @@
   BOMB_RADIUS_GRID: 1.5,   // 爆風半径（グリッド単位、円形当たり判定）
   BOMB_FUSE_MS: 1000,      // 設置から爆発までの時間（ms）
   BOMB_COOLDOWN_MS: 1200,  // 設置後に次の爆弾を置けるまでの待機時間（ms）
+  BOMB_DEDUP_EXTRA_TTL_MS: 1000, // 重複排除保持時間の追加分（ms）
 
   // チーム設定（クライアント/サーバー契約）
   TEAM_COUNT: 4,