In a mobile communication system which comprises a mobile station (1), a radio network (2) for radio transmission and reception to and from the mobile station, a home location register (HLR) (4) for managing, through a mobile services-switching center (3), current location information representative of a current location of the mobile station in a public telephone network, and a home agent (HA) (7) for managing, through a packet gateway (6), current location information representative of a current location of the mobile station in a packet data communication network, the home location register and the home agent are connected to each other through a communication channel (15) for transmission of update contents for the current location information managed by the home location register and the home agent. The home location register and the home agent are provided with location information update units (13, 14) responsive to the update contents for updating the current location information managed by the home location register and the home agent, respectively.