In an access gateway (AGW) comprising a C-AGW for handling control messages and a plurality of U-AGWs for handling data packets, when a tunnel setup request is issued from one of base stations to hand over a mobile station, the C-AGW selects a new U-AGW being in the lowest load status out of the U-AGWs, estimates the load status of the new U-AGW in the case of changing the tunnel endpoint for the mobile station from a current U-AGW to the new U-AGW. The C-AGW designates the new U-AGW as the tunnel endpoint for the mobile station if the estimated load status satisfies a predetermined condition, but designates the current U-AGW as the tunnel endpoint if the estimated load status does not satisfy the predetermined condition.