PROBLEM TO BE SOLVED: To provide an apparatus for compensating distortion caused by a pre-distortion system capable of reducing third distortion caused by an amplifier for amplifying an amplification object signal comprising a plurality of frequency components and enhancing the unbalance between upper side third distortion and lower side third distortion caused by the amplifier. SOLUTION: A phase distortion generating means 8 at a pre-stage of the amplifier 10 generates phase distortion on the basis of a phase distortion control signal to the amplification object signal, an amplitude distortion generating means 9 at a pre-stage of the amplifier 10 produces amplitude distortion on the basis of the amplitude distortion control signal to the amplification object signal, and control signal supply means 3, 4, 5a, 5b, 6a, 6b, 16, 7a, 7b supply the phase distortion control signal with a difference frequency component of the amplification object signal and synchronously with the level of the amplification object signal at zero phase difference and the amplitude distortion control signal with the difference frequency component of the amplification object signal synchronously with the level of the amplification object signal at a non- zero phase difference. COPYRIGHT: (C)2003,JPO