To provide a device and a method to process sound signal phase information in which identification is made for important phase components considering the hearing characteristics of a human being so that coding or synthesis of the phase components of sound signals are selectively conducted.

The device consists of a critical bandwidth computing section 100, which obtains a critical bandwidth for various frequencies in accordance with the bandwidth characteristics of a human hearing filter, a frequency range setting section 102, which sets the frequency range of a local phase change using the critical bandwidth obtained by multiplying the critical bandwidth by a prescribed scaling coefficient and correcting the product, and a phase importance discriminating section which checks whether the frequency components adjacent to the above frequency belongs to the frequency range corresponding to the above frequency for every frequency and judges whether the phase of the signals having the above frequency components is important from the viewpoint of hearing characteristics.