Even if “UE category” is notified of only in an uplink (or a downlink), a radio base station eNB can suitably perform a communication control on a mobile station UE in the downlink (or the uplink) for which “UE category” is not notified of. In the mobile station UE according to the present invention, when the mobile station UE does not support “UE category for Release-12” in the uplink, a transmitting unit 12 does not notify of “UE category for Release-12” corresponding to the uplink, and when the mobile station UE does not support “UE category for Release-12” in the downlink, the transmitting unit 12 does not notify of “UE category for Release-12” corresponding to the downlink.