An authentication device comprising: a registration feature data storage unit that is configured to store biometric information of a user as registration data; an authentication unit that is configured to perform authentication processing by collating input data which is biometric information input by the user, and registration data which is stored in the registration feature data storage unit; an authentication history storage unit that is configured to store an authentication result authenticated by the authentication unit as history information with date and time; a prediction unit that is configured to acquire authentication results over a long-term from the authentication history storage unit, to calculate authentication rates of successful authentication using authentication results acquired, to calculate a temporal variation of authentication rates of predetermined periods, and to predict a future authentication rate based on the temporal variations of authentication rates calculated; and an updating unit that is configured to update registration data stored in the registration feature data storage unit based on the input data when it is predicted by the prediction unit that a future authentication rate will be lower than a first threshold value Y wherein the prediction unit is configured to predict a future authentication rate will be lower than the first threshold value γ when a degree of similarity, between a temporal variation of an authentication rate from a first past time point which is a first time period ago from a current time point to the current time point and from a second past time point which is the first time period ago from a third past time point which is one year ago from the current time point to the third past time point is higher than a second threshold value, and the authentication rate from the third past time point to a fourth past time point which is a second time period after the third past time point, is determined to be lower than the first threshold value γ. a registration feature data storage unit that is configured to store biometric information of a user as registration data; an authentication unit that is configured to perform authentication processing by collating input data which is biometric information input by the user, and registration data which is stored in the registration feature data storage unit; an authentication history storage unit that is configured to store an authentication result authenticated by the authentication unit as history information with date and time; a prediction unit that is configured to acquire authentication results over a long-term from the authentication history storage unit, to calculate authentication rates of successful authentication using authentication results acquired, to calculate a temporal variation of authentication rates of predetermined periods, and to predict a future authentication rate based on the temporal variations of authentication rates calculated; and an updating unit that is configured to update registration data stored in the registration feature data storage unit based on the input data when it is predicted by the prediction unit that a future authentication rate will be lower than a first threshold value Y wherein the prediction unit is configured to predict a future authentication rate will be lower than the first threshold value γ when a degree of similarity, between a temporal variation of an authentication rate from a first past time point which is a first time period ago from a current time point to the current time point and from a second past time point which is the first time period ago from a third past time point which is one year ago from the current time point to the third past time point is higher than a second threshold value, and the authentication rate from the third past time point to a fourth past time point which is a second time period after the third past time point, is determined to be lower than the first threshold value γ.