In CA performed using three or more frequency bands, whether or not a mobile station UE is capable of performing an inter-frequency measurement without a gap is properly determined. The mobile station UE according to the invention includes a transmission unit 11 configured to transmit “UE Capability” indicating a capability of the mobile station UE to a radio base station eNB. The transmission unit 11 is configured to notify frequency bands in which the mobile station UE is capable of performing an inter-frequency measurement without a gap for each “CA band combination” as the “UE Capability”.