To provide a personal authentication device allowing dictionary registration and dictionary updating without imparting a burden onto an authenticated person, and precluded the authenticated person from feeling complexity for initial introduction.

An authentication data input part 103 acquires a data for a dictionary from an authenticated person 100. A dictionary registration and updating part 104 prepares the dictionary for authentication based on the acquired data for the dictotinary, and stores it in a dictionary storage part 101. Then, a data for an authentication test is acquired from the authenticated person 100 by the authentication data input part 103 to conduct the authentication test. An authentication part 102 conducts the authentication test whether the authenticated person 100 is the person itself or not, using the acquired data for the authentication test and the dictionary stored in the dictionary storage part 101. When the person itself is authenticated correctly by the authentication test, the dictionary registration and updating part 104 prepares a new dictionary again based on the data for the dictionary acquired by the authentication data input part 103 and the data for the authentication test, and stores it in the dictionary storage part 101 as a regular dictionary.