Surround-effect, providing no unnatural feeling to the listeners who sit next to each other under side-by-side basis through virtual sound sources, is realized. A surround left channel signal SL and a surround right channel signal SR are mixed with an adder 10 and are in monaural. A first monophonic signal and a second monophonic signal thus resulted are supplied to a virtual localization processor 12. A first virtual localization output of the processor 12 is supplied to a front left speaker SPL and a front right speaker SPR and a second virtual localization output thereof is supplied to a front center speaker SPC. In this way, virtual sound sources can be created at the right and the left to the listener 2. Similarly, virtual sound sources can also be created at the right and the left to the listener 3. Sound fields from the virtual surround sources are in reverse to the listener 2 and the listener 3. However, no substantial drawbacks caused by the reversal are observed because monophonic signals are reproduced as the surround signals in this embodiment. In this way, surround-effect with natural feeling can be achieved.