The collating device includes the Formant estimation section that estimates feature amount data that represents a time-based change in frequencies of first and second Formants from voice data input through the microphone. The difference computing section calculates a difference between some reference feature amount data and the feature amount data as the feature-amount difference data. This feature-amount difference data is stored in a database. The feature-amount difference data corresponding to voice data input upon collation is collated with the feature-amount difference data registered in the database, and the result is output.