A relay gateway apparatus HO-GW is provided between heterogeneous access networks (a WiMAX access network and a UMB access network). The HO-GW performs conversion of a movement control signal (an Inter-AGW handover control signal) and relay of communication data. When the relay is performed, user data from a CN reaches a wireless terminal MN through an HA of a core network, an access router ASN-GW, the HO-GW, and a base station eBS.