1. A pattern recognition apparatus for recognizing an input pattern with respect to a plurality of reference patterns, comprising: storage means for storing the input pattern data; receiving means for receiving the plurality of reference pattern data; similarity calculating means for calculating similarities between the input pattern data stored in the storing means and each of the reference pattern data received by the receiving means to acquire similarity values, the similarity calculating means including a plurality of product calculating circuits, each for calculating a corresponding product data based upon products of the input pattern data and a corresponding one of the reference pattern data and a plurality of sum calculating circuits, each for calculating a sum of the corresponding product data as a similarity value; a floating operation circuit to floating-process the similarity values corresponding to the plurality of reference pattern data acquired by the similarity calculating means in an exponent indication; and sorting means for sorting the similarity values which have been floating-processed by the floating operation circuit in an order of magnitude of the similarity values so as to obtain a candidate pattern, wherein the sorting means comprises: a first register for storing a selected one of the similarity values which has been floating-processed by the floating operation circuit; a second register for storing the sorted similarity values, wherein the second register includes a plurality of memories which are capable of performing a data shifting operation; comparing means for comparing the selected one of the similarity values stored in the first register with the sorted similarity values stored in the second register, and for selecting, based upon the order of similarity values already stored in the second register, one of the memories for storing the selected one of the similarity values stored in the first register; and control means for simultaneously shifting at least one of the sorted similarity values stored in the second register in accordance with order of similarity values already stored in the second register, causing the second register to store the similarity value compared by the comparing means in the selected one of the memories, and holding the sorted similarity value stored in the selected one of the memories in accordance with the comparison performed by the comparing means.