A noise suppression apparatus calculates a sound spectrum and a noise spectrum from an input sound, further calculates gain based on the sound spectrum and noise spectrum, and suppresses noise in the input sound. The noise suppression apparatus includes a first frame-dividing unit that divides the input sound into frames having a predetermined frame length, a second frame-dividing unit that divides the input sound into frames having a longer frame length than the frame length of the first frame-dividing unit, a second converting unit that converts, into a spectrum, the input sound divided into frames by the second frame-dividing unit, a smoothing unit that smoothes the converted spectrum in a frequency direction, and a gain calculating unit that calculates gain based on the smoothed spectrum and the noise spectrum.