A 1:N identification system having high convenience and safety is to be provided. An authentication client includes at least one biometric information input sensor and a feature extraction function. A database includes an enrollee ID and registered templates of biometric information of at least one kind every enrollee and includes a score table. An authentication server includes a prior probability setting function, a 1:N fast matching function for successively matching the feature with the registered templates of the enrollees and discontinuing matching processing when the number of times of matching has exceeded a predetermined threshold, a delta score calculation function for calculating a delta score by using a score obtained by the 1:N fast matching and using the score table, a posterior probability calculation function for calculating posterior probabilities respectively of the enrollees on the basis of the score and the delta score, and an authentication object user identification function.