Abstract: A nonlinear compensator comprising a signal processing section, a distortion detecting section, and a distortion correcting section. The signal processing section detects the time difference and phase difference between two signals by calculating correlation, synchronizes the two signals with each other, and causes the phase of one signal to coincide with that of the other. The distortion detecting section determines an amplitude error and a phase error in the two signals and inputs the errors as distortion components to a distortion correcting section. The distortion correcting section sequentially selects the amplitude, the phase, and the amount of compensation corresponding to the value of the amplitude from the amounts of compensation registered at the initial stage and updated adaptively, and adds the amount of compensation to the digital base band signal obtained at the input demodulation section to compensate for the distortion components.