PURPOSE: To prevent the error recognition of voice data with a strong ambient noise and ambient noise superposed by detecting and rejecting the ambient noise.

CONSTITUTION: This unit consists of voice collecting microphone 10, voice period determination part 20 which determines a voice period by examining the amplitude level of an input signal, recognition processing part 30 which determines a recognition result by analyzing and discriminating a signal in the voice period, ambient- noise collecting microphone 40, noise detection part 50 which detects a strong noise signal by examining the amplitude level of a noise signal, and rejection processing part 60 which rejects the recognition result determined by processing part 30 when the strong noise is detected in the voice period. As a result, when a noise is superposed upon an input voice, the generation of an ambient noise is detected and it is rejected.