1. An identification apparatus comprising: a classification unit that determines two or more classes into which input biometric data is classified out of a plurality of classes based on features of the input biometric data, where a plurality of items of registered biometric data have been classified into at least one of the plurality of classes; a calculation unit that calculates similarity between the input biometric data and each item of the registered biometric data registered in each of the two or more classes into which the input biometric data is classified; and an identification unit that identifies data on a user who has entered the input biometric data among the registered biometric data registered in any of the two or more classes, based on the similarity to the input biometric data.