1. A speech processing apparatus for processing an input utterance and registering a word contained in the input utterance on the basis of the processing result, comprising: recognition means for recognizing the input utterance; unknown word determination means for determining whether the recognition result of the input utterance obtained by the recognition means contains an unknown word; recognition result rejection means for determining whether the recognition result determined by the unknown word determination means to contain an unknown word is rejected or not; and word extracting means for acquiring a word corresponding to the unknown word contained in the recognition result determined not to be rejected by the recognition result rejection means.