When a relay station load, which is the load of communications with radio terminals (300E-300G), of a relay node (200) exceeds a load allowable amount, which is determined according to the load of a radio base station (100A), the relay node transmits a handover request, which requests permission for a relay handover, to the radio base station (100A) and performs a relay handover if the relay node receives a handover command which instructs a relay handover.