A communication apparatus according to the present invention is provided with a mobile station 10, a packet transfer apparatus 50, and an access point 70 which relays between the mobile station 10 and the packet transfer apparatus 50. The cellular side access point 70 transmits a tunnel switch request to the second radio network area, when an authentication processing for establishing a secured connection between the mobile station and the second radio network succeeds, and when the mobile station changes from the first radio network area to the second radio network area.