To equalize the output distortion of an output-stage high-frequency amplifier (232) of a communication device, a modulator comprises a digital filter (11) for sampling binary input data at a rate that is N times the symbol rate (N is an integer of two or more) to convert the binary input data into multinary data other than binary data and outputs the multinary data and a nonlinear equalizer (12) for overcompensating the output of the digital filter with a previously-measured nonlinear distortion of the output of the high-frequency amplifier.
