In additional enrollment of a template in a biometric authentication system, the template is automatically enrolled on the basis of a plurality of authentication results to assure a user's convenience and security. A post-migration authentication server receives a first template and a second template from a post-migration authentication terminal, performs authentication on the basis of the comparison result between the received first template and the user's preliminarily first enrolled template, and provisionally enrolls the first template and the second template. It repeats the reception, authentication, and provisional enrollment and calculates a match probability from a plurality of comparison results of the provisionally first enrolled templates, determines whether or not to store a second enrolled template on the basis of the match probability, and automatically enrolls the second template in the post-migration authentication server.