A mobile station apparatus performs communication with abase station apparatus using a multiple number of component frequency bands, each being a band having a predetermined frequency bandwidth, and includes: a controller setting up a value relating to the transmission power of each component frequency band in accordance with the number of component frequency bands to which radio resources are allocated; and a transmission processor adjusting the transmission power of each component frequency band, based on the value of transmission power set at the controller and transmitting a signal using radio resources of a multiple number of component frequency bands. With this configuration, in a radio communication system using a multiple number of component frequency bands, it is possible to adjust transmission power control in accordance with the number of uplink component frequency bands used for transmission and transmit a signal of a waveform suitable for the radio communication system.