A service apparatus for a public and private mobile communication network in a mobile communication service system including a public mobile communication network and a private mobile communication network. The service apparatus includes a device for connecting a public mobile communication service system to a private mobile communication service system, and providing a mobile station in a predetermined service area with both a public mobile communication service and a private mobile communication service. The device includes a base station transceiver subsystem (BTS) located in the predetermined service area, for forming a radio channel to the mobile station in the service area; a communication path provider connected to the BTS, a base station controller (BSC) in the public mobile communication service system and a mobile switching center (MSC) of the private mobile communication service system, said communication path provider providing a communication path for transmitting data of the service system and data of the BTS; and a call manager for distinguishing the public mobile communication service from the private mobile communication service by analyzing data received through the communication path, and performing call management for the corresponding service.