Provided is a mobile station device capable of performing RACH transmission with a small amount of resources. In this device, a RACH generating unit (111) is formed by a signature selection unit (112) and a modulation unit (113). A RACH signal is generated as follows. That is, according to inputted RACH re-transmission quantity information, the signature selection unit (112) selects one code sequence as a signature from a plurality of different code sequences. The modulation unit (113) modulates the signature (code sequence) and generates a RACH signal. A multiplexing unit (116) time-multiplexes the RACH signal inputted from the modulation unit (113) and user data inputted from the modulation unit (115). A radio transmission unit (117) subjects the multiplexed signal to radio processing and transmits it via an antenna (121).