1. A speech recognition apparatus comprising: parameter generating means for sequentially generating acoustic parameter data corresponding to input speech; data generating means for detecting a segment in which each discrete phonetic symbol exists on the basis of acoustic parameter data from said parameter generating means and generating phonetic symbol data corresponding to at least one reference phonetic symbol having a similarity larger than a predetermined value with respect to the discrete phonetic symbol in each segment and score data corresponding to the similarity; memory means for storing the phonetic symbol data and score data from said data generating means; coefficient generating means connected to said parameter generating means and data generating means and for generating compatability coefficient between phonetic symbols generated in two continuous segments; updating means for updating plural times the score data in said memory means with compatibility coefficient relating to the corresponding phonetic symbol data as a function; and recognition means for sequentially reading out from said memory means phonetic symbol data having the maximum score data in each segment after the updating process is finished, and then recognizing the sequence of phonetic symbol data.