To provide an acoustic signal compressor for conducting level compression in high quality for an acoustic signal having a large dynamic range.

The acoustic signal compressor comprises a delay means 1 for delaying an input acoustic signal by a first time duration Δt1; and a gain control means 2 arranged at the next stage of the delay means for controlling that gain decreases in monotone from a point of time, when the level of an input acoustic signal reaches a value established beforehand, and then, when the level of an input acoustic signal reaches a peak, the gain holds a value at the point of time for a second time duration Δt2, and then that the gain increases in monotone to return to an original gain.