A speaker identifying apparatus includes: a module for performing a principal component analysis on predetermined vocal tract geometrical parameters of a plurality of speakers and calculating an average and principal component vectors representing speaker-dependent variation; a module for performing acoustic analysis on the speech data being uttered for each of the speakers to calculate cepstrum coefficients; a module for calculating principal component coefficients for approximating the vocal tract geometrical parameter of each of the plurality of speakers by a linear sum of principal component coefficients; a module for determining, by multiple regression analysis, a coefficient sequence for estimating principal component coefficients by a linear sum of the plurality of prescribed features, for each of the plurality of speakers; a module for calculating a plurality of features from speech data of the speaker to be identified, and estimating principal component coefficients for calculating the vocal tract geometrical parameter of the speaker to be identified, by a linear sum obtained by applying the coefficient sequence calculated by the regression analyzing module; and a module for identifying said speaker to be identified, by comparing the estimated principal component coefficients with the principal component coefficients calculated for each of the plurality of speakers by the principal component coefficient calculating module.