1. A method, carried out by use of a keyword locating apparatus for locating a keyword contained in a recognition target speech, comprising: by extracting feature parameters from frames constituting the recognition target speech, forming a feature parameter vector sequence that represents the recognition target speech; by normalizing of the feature parameter vector sequence with use of a codebook containing a plurality of codebook vectors, obtaining a feature trace of the recognition target speech in a vector space; and specifying the position of a keyword by matching prestored keyword template traces with the feature trace, wherein the normalizing step includes the step of obtaining the feature trace by extracting representative feature parameter vectors from the feature parameter vector sequence, and the step of extracting the representative feature parameter vectors includes the steps of: searching the codebook for codebook vectors that are closest to the feature parameter vectors; indicating the feature parameter vectors with use of numbers of the codebook vectors thus found; and obtaining the feature trace by combining feature parameter vectors represented by continuously identical codebook vectors.