Provided is a noise-robust voice activity segmentation device which updates parameters used in the determination of voice-active segments without burdening the user, and also provided are a voice activity segmentation method and a voice activity segmentation program.The voice activity segmentation device comprises: a first voice activity segmentation means for determining a voice-active segment (first voice-active segment) and a voice-inactive segment (first voice-inactive segment) in a time-series of input sound by comparing a threshold value and a feature value of the time-series of the input sound; a second voice activity segmentation means for determining, after a reference speech acquired from a reference speech storage means has been superimposed on a time-series of the first voice-inactive segment, a voice-active segment and a voice-inactive segment in the time-series of the superimposed first voice-inactive segment by comparing the threshold value and a feature value of the time-series of the superimposed first voice-inactive segment; and a threshold value update means for updating the threshold value in such a way that a discrepancy rate between the determination result of the second voice activity segmentation means and a correct segmentation calculated from the reference speech is decreased.