A radio base station according to the present invention comprising: a mobile communication system, a relay node and a first radio base station are connected via a radio bearer, the first radio base station and a second radio base station are connected, a mobile station is configured to perform a handover process between a state in which a radio bearer is set with the relay node so as to communicate via the relay node and the first radio base station, and a state in which a radio bearer is set with the second radio base station so as to communicate via the second radio base station, and the handover process is configured such that a radio bearer is set between the relay node and the second radio base station, and the control signals involved in the handover process are sent and received via the radio bearer that has been set between the relay node and the second radio base station.