1. A pattern recognition apparatus for recognizing a pattern of time serial unclassified input data by classifying the unclassified input data as one of a predetermined number of classes, the apparatus comprising: framing means for sequentially extracting a plurality of frames from the unclassified input data at predetermined frame intervals, the unclassified input data being speech data, and for outputting the extracted data as frame data; calculating means for calculating an average vector and a variance matrix as a feature distribution parameter including an average vector and a variance matrix for each frame of the plurality of frames extracted from the unclassified input data, said feature distribution parameter representing a distribution obtained when the frame data is mapped to a space of a feature quantity of the unclassified input data; and classifying means for classifying a series of the feature distribution parameters as one of the predetermined number of classes, wherein the classifying means includes means for judging, using a hidden Markov model method, which of the predetermined number of classes to which the series of the feature distribution parameters belongs.