An authentication processing apparatus for performing authentication based on a user's normal operation is provided. The authentication processing apparatus performs the authentication processing on the basis of operation information obtained from normally operating an information processing apparatus. Operation information obtained from operating an input unit by the user, such as a keyboard inputting mode, is obtained to serve as operation information, and the obtained operation information is checked against operation information registered in a database to perform authentication. Authentication is thus made possible without requiring the user to perform the special input processing for the authentication processing. Authentication is performed taking into consideration a plurality of pieces of operation information. With the checking processing in which less dispersed data is weighted, user authentication with high accuracy is made possible.