Information entered by a user at the time of logging on is also used in a check to be performed in response to a request for use/edit of a program or data related to an additional function. Authentication information of the user using a program or data related to the additional function is included in advance in the program or data, so that, when the user has made a request for using/edit the program or data, it is checked whether or not the user is a user authorized to use the additional function, using the information entered by the user at the time of logging on and the authentication information. To perform user management for creating an account of a user using an apparatus or software and setting authorization of a user in using the apparatus or software, a plurality of users have parent-child relationships with a highest-position, root user at the top. Each user as a parent is allowed to add a child user, and each parent user is allowed to set authorization of a user lower in hierarchical position than the child user. The parent-child relationships of the users are displayed on a display. Each of the users can give any settable user authorization equal to or lower than its own user authorization.