A Fourier transform unit (111) performs Fourier transform on a digital signal on a time axis to generate a frequency domain signal which is a signal on a frequency axis. A filter unit (113) equalizes the frequency domain signal in a frequency domain using N first coefficients. An inverse Fourier transform unit (112) performs inverse Fourier transform on the frequency domain signal processed by the filter unit (113) and returns the frequency domain signal to the digital signal on the time axis. That is, the Fourier transform unit (111), the inverse Fourier transform unit (112), and the filter unit (113) compensate for waveform distortion included in the digital signal using an equalization process (that is, frequency-domain equalization (FDE)) in the frequency domain. A first coefficient setting unit (114) sets N first coefficients used by the filter unit (113) using m (provided N>m) second coefficients.