An apparatus of this invention stably separates a sound source even when the relative positional relationship between the sound source and a sound pickup device has changed. This apparatus includes a sound pickup unit configured to pick up sound signals of a plurality of channels, a detector configured to detect a change in a relative positional relationship between a sound source and the sound pickup unit, a phase regulator configured to regulate a phase of the sound signal in accordance with the relative position change amount detected by the detector, a parameter estimator configured to estimate a variance and spatial correlation matrix of a sound source signal as sound source separation parameters with respect to the phase-regulated sound signal, and a sound source separator configured to generate a separation filter from the estimated parameters, and perform sound source separation.
