Distortion compensation coefficients for correcting distortion of a transmission power amplifier are stored in a memory beforehand, a distortion compensation coefficient conforming to powers or amplitudes of a present transmit signal and a past transmit signal is read out of the memory, and distortion compensation processing is applied to the transmit signal using this distortion compensation coefficient. The transmit signal thus subjected to distortion compensation processing is then amplified by the transmission power amplifier and the amplified signal is transmitted, and the distortion compensation coefficient is updated based upon the transmit signal before distortion compensation and an output signal from the transmission power amplifier.