1. A voice recognition system comprising: a signal processing unit for converting inputted speech voice data into a feature; an acoustic model storing unit in which an acoustic model obtained by modeling what kind of feature a voice tends to become is stored in advance; a vocabulary dictionary storing unit in which information of a recognition vocabulary is stored in advance; a voice section detecting unit for detecting voice sections in the speech voice data according to a predetermined voice section criterion; a priority determining unit for selecting a voice section to be given priority from among the voice sections detected by the voice section detecting unit according to a predetermined priority criterion; a decoder for calculating a degree of matching with the recognition vocabulary using the feature of the voice section selected by the priority determining unit and the acoustic model; and a result output unit for outputting a word sequence having the best score in the matching by the decoder as a recognition result; wherein the priority determining unit uses as the predetermined priority criterion at least one selected from the group consisting of (1) a length of the voice section, (2) a power or an S/N ratio of the voice section, and (3) a chronological order of the voice section.