A radio base station includes a mobile communication system configured to transmit and receive a data signal between a mobile station and a gateway device via a relay node and a radio base station. The mobile communication system is configured such that the radio bearer for the mobile station is set between the mobile station and the relay node. The radio bearer for the relay node is set between the relay node and the radio base station. A network bearer for the mobile station is set between the relay node and the gateway device. The network bearer for a plurality of mobile stations is multiplexed in the radio bearer for the relay node, and a data signal is transmitted and received between the mobile station and the gateway device via the radio bearer for the mobile station and the network bearer for the mobile station.