diff --git a/apiServer/src/main/protobuf/room.proto b/apiServer/src/main/protobuf/room.proto
index e976555..2d753b9 100644
--- a/apiServer/src/main/protobuf/room.proto
+++ b/apiServer/src/main/protobuf/room.proto
@@ -81,6 +81,10 @@ message SendResultRequest {
     repeated Coordinate ghostRecord = 3;
 }
 
+message GetPublicRoomResponse {
+    int32 vagrantRoom = 1;
+}
+
 message Empty {}
 
 service RoomService {
@@ -94,6 +98,9 @@ service RoomService {
     rpc ParentOperation(ParentOperationRequest) returns (stream Operation) {};
 
     rpc SendResult(SendResultRequest) returns (Empty) {};
+
+    // まだ埋まっていない公開部屋数
+    rpc GetPublicRoom(Empty) returns (GetPublicRoomResponse) {};
 }
 
 
diff --git a/apiServer/src/main/scala/com/github/CA21engineer/HouseHackathonUnityServer/service/RoomAggregates.scala b/apiServer/src/main/scala/com/github/CA21engineer/HouseHackathonUnityServer/service/RoomAggregates.scala
index 77ef62a..92ecab9 100644
--- a/apiServer/src/main/scala/com/github/CA21engineer/HouseHackathonUnityServer/service/RoomAggregates.scala
+++ b/apiServer/src/main/scala/com/github/CA21engineer/HouseHackathonUnityServer/service/RoomAggregates.scala
@@ -111,5 +111,12 @@ class RoomAggregates[T, Coordinate, Operation](implicit materializer: Materializ
       source
     }
 
+  def getPublicRoom: Int = {
+    this.rooms.count { room =>
+      // 埋まっていない && パブリック
+      !room._2.isFull && room._2.roomKey.isEmpty
+    }
+  }
+
 }
 
diff --git a/apiServer/src/main/scala/com/github/CA21engineer/HouseHackathonUnityServer/service/RoomServicePowerApiImpl.scala b/apiServer/src/main/scala/com/github/CA21engineer/HouseHackathonUnityServer/service/RoomServicePowerApiImpl.scala
index cd5cabc..7f5bffd 100644
--- a/apiServer/src/main/scala/com/github/CA21engineer/HouseHackathonUnityServer/service/RoomServicePowerApiImpl.scala
+++ b/apiServer/src/main/scala/com/github/CA21engineer/HouseHackathonUnityServer/service/RoomServicePowerApiImpl.scala
@@ -74,4 +74,10 @@ class RoomServicePowerApiImpl(implicit materializer: Materializer) extends RoomS
       }
       .fold(Future.failed[Empty](new Exception("Internal Error!!!")))(_ => Future.successful(Empty()))
   }
+
+  // まだ埋まっていない公開部屋数
+  override def getPublicRoom(in: Empty, metadata: Metadata): Future[GetPublicRoomResponse] = {
+    Future.successful(GetPublicRoomResponse(roomAggregates.getPublicRoom))
+  }
+
 }