A delta-sigma modulator and delta-sigma modulation method according to the present invention are capable of ensuring a stable 1-bit signal having less distortion at the transition time from an audio signal reproduction state to soundless state while maintaining high sound quality during reproduction of an audio signal representing music or the like, and, at the same time, capable of maintaining high sound quality at the transition time from a soundless state to audio signal reproduction state. The delta-sigma modulator applies delta-sigma modulation to an input signal to output a 1-bit digital signal, and comprises an integration section that applies integration to the input signal, a quantization section that quantizes the integrated output from the integration section, a random noise generation section that generates a random noise signal whose gain has been adjusted based on the integrated output of the integration section, a detection section that detects a predetermined pattern from the input signal, and a changeover section that switches supply and suspension of supply of the random noise signal from the random noise generation section to the quantization section based on a detection result of the detection section.