A frequency domain filter receives an input signal in a frequency domain being blocked by an overlap-save method. The frequency domain filter multiplies the input signal in the frequency domain by a coefficient for each frequency. A coefficient updating unit adaptively updates a filter coefficient of the frequency domain filter. A constraint operation unit performs an operation of a constraint on a filter coefficient of the frequency domain filter in such a way as not to be affected by distortion caused by wraparound from both ends of a block to the output signal. A frequency at which the constraint operation unit performs the operation of the constraint is lower than a frequency at which the coefficient updating unit adaptively updates the filter coefficient of the frequency domain filter.