It is intended to achieve a user authentication system capable of forcibly presenting a content to a user. Provided is a content presentation-type authentication system designed to allow a client to perform a content presentation-type user authentication in which user authentication is performed in such a manner that a plurality of pattern elements arranged in a given pattern are presented as a presentation pattern to a user who intends to be authenticated, and a one-time password derivation rule is used as a password of the user and applied to certain ones of the pattern elements located at specific positions in the presentation pattern to create a one-time password, and a content is forcibly presented to the user in connection with the user authentication. The content presentation-type authentication system comprises an authentication-service providing server configured to manage respective user IDs and passwords of users, content data indicative of a detail of each of a plurality of contents, and respective content IDs of the plurality of contents, and provide content-added authentication information to each of the users, and a client having a content presentation-type user authentication program and a processor.