PURPOSE: To reproduce a sound field according to diversified listeners' favorites by inputting one channel signal to each phase shifter whose phase center frequency can be varied and set continuously and adding the output signal of each phase shifter and the other channel signal respectively.

CONSTITUTION: When the phase center frequency f0 is set to a certain value F0 within a variable range, the phase shifters 2 and 3 output an R signal and an L signal which are in phase with an input signal according to the frequencies of the R channel signal and L channel signal inputted to the phase shifters 2 and 3. Thus, the phase center frequency f0 of the phase shifters 2 and 3 are varied and set according to listeners' favorites and then signal components from a difference component L-R to a sum signal component L+R or opposite- phase sum signal component -(L+R) are outputted as L-side and R-side surround signals from a noninverting amplifying circuit 6 and an inverting amplifying circuit 7 respectively, thereby reproducing the sound field corresponding to the diversified listeners' favorites.