A wireless communication system includes a relay station, first and second wireless base stations, a gateway device, and a mobile station. The gateway device is connected to the first and second wireless base stations by a cable. The first and second wireless base stations are interconnected by a cable. The relay station is connected wirelessly to the first wireless base station to perform relayed communication via the first wireless base station. When the mobile station at a lower level than the relay station executes handover to the second wireless base station, the first wireless base station switches a data transfer route by redirecting data which is not yet completely transmitted to the mobile station, to be forwarded to the second wireless base station.