<p>A distortion compensating device comprises a 3dB coupler having four terminals. The first terminal supplies an input signal to be inputted to an amplifier or is supplied with an input signal from an amplifier. The second terminal is associated with a third-order distortion generator for generating a third-order distortion having an amplitude for canceling out a third-order distortion generated by the amplifier depending on the supplied input signal. The third terminal is associated with a phase adjuster for adjusting the phase of the input signal to set the phase difference between the input signal and the third-order distortion generated by the third-order distortion generator to a phase difference for canceling out the third-order distortion generated by the amplifier. The fourth terminal combines and outputs the third-order distortion generated by the third-order distortion generator and the input signal whose phase is adjusted by the phase adjuster for compensating for the third-order distortion generated by the amplifier.</p>
