A user authentication device includes a user authentication setter that enables or disables a predetermined plurality of authentication methods, and a user authenticator that accepts user authentication by the authentication method that the user authentication setter enables, and a controller that controls the user authentication setter and the user authenticator. When the user authentication setter accepts a setting that enables a single authentication method among the plurality of authentication methods, the controller controls the user authentication setter to disable all authentication methods other than the single authentication method, and the user authenticator accepts only user authentication by the single authentication method.