An object is to increase opportunities for starting “Inter-band CA”. A mobile station UE of the present invention includes a transmission unit 14 configured to postpone transmission of a random access preamble in a cell #2 when the mobile station UE in a “RRC_Connected state” in a cell #1 detects a start trigger of a random access procedure in the cell #2, and determines that an uplink signal is being transmitted in the cell #1. The transmission unit 14 performs the postponed transmission of the random access preamble upon completing the transmission of the uplink signal in the cell #1.