PURPOSE: To provide the surround stereo having a sense of spread and a surround effect without limiting an input signal with simplified configuration.

CONSTITUTION: First and second time delay means 11, 12 form a time difference till a signal from a speaker arranged at the side of a listener reaches to left and right ears of the listener. A 1st equalizer means 13 forms a frequency characteristic difference of each signal reaching the left and right ears of the listener from the speaker arranged aside the listener. A 1st phase inversion means 15 erases or attenuates a signal being a crosstalk from the speaker to the left and right ears of the listener together with the 1st time delay means 11 and the 1st equalizer means 13. A 2nd phase inversion means 16 forms a pseudo stereo sound based on the operation above.