To perform automatic gain control for adjusting a level of an audio signal to be fixed when the level of the input audio signal is varied, and to hardly fluctuate a noise component.

There are provided gain control means 11, 12 for controlling the gain of an input audio signal S1; a noise suppression amount calculation unit 13 for calculating a noise suppression amount SL for the audio signal; a correction unit 14 for correcting the noise suppression amount SL on the basis of a gain GL calculated in the gain control means; and a noise suppression unit 15 for suppressing a noise component contained in the audio signal in accordance with the corrected noise suppression amount SLH.