A voice intensifier capable of reducing abrupt changes in the amplification factor between frames and realizing excellent sound quality with less noise feeling by dividing input voices into the sound source characteristic and the vocal tract characteristic, so as to individually intensify the sound source characteristic and the vocal tract characteristic and then synthesize them before being output. The voice intensifier comprises a signal separation unit for separating the input sound signal into the sound source characteristic and the vocal tract characteristic, a characteristic extraction unit for extracting characteristic information from the vocal tract characteristic, a corrective vocal tract characteristic calculation unit for obtaining vocal tract characteristic correction information from the vocal tract characteristic and the characteristic information, a vocal tract characteristic correction unit for correcting the vocal tract characteristic by using the vocal tract characteristic correction information, and a signal synthesizing means for synthesizing the corrective vocal tract characteristic from the vocal tract characteristic correction unit and the sound source characteristic, so that the sound synthesized by the signal synthesizing means is output.