1. A voice recognition device for executing noise adaptation processing based on a noise model on an input voice signal to carry out voice recognition on the input voice signal is characterized by comprising: first storage means for calculating a first parameter representative of plural noise models contained in each of plural noise environmental categories in advance and storing the first parameter for every noise environmental category; second storage means for calculating a second parameter representing relative positional information between each of the plural noise models and the first parameter in advance and storing the second parameter; estimating means for estimating, on the basis of the characteristic of an environmental noise superposed by the input voice signal, a noise environmental category to which the environmental noise concerned belongs; selecting means for selecting and extracting the first parameter corresponding to a noise environmental category estimated by the estimating means from the first storage means; and noise adaptation means for restoring a noise model adaptive to the environmental noise by using the first parameter extracted by the selecting means and the second parameter read out from the second storage means and executing noise adaptation processing on the input voice signal by using the noise model thus restored.