To register words in a document file described in free format and containing words desired to be added to a voice recognition dictionary.

An unknown word registration device 11 reads a document file 10 containing unknown words, extracts words by carrying out morpheme analysis or the like, and extracts words which do not exist in the voice recognition dictionary 13 as unknown words. The extracted unknown words are listed and displayed and, after the unknown words and the reading and parts of speech imparted to the unknown words are corrected or deleted by a user, the selected unknown words are registered in a batch in the voice recognition dictionary 13.