Access control system, access managing method, image forming device and computer program product

A multifunction device includes a storage controlling portion for causing document data, which are to be given by a user who has logged in to a different user, to be stored in a box owned by the different user, and an access authority setting portion for granting an access authority to make access to the document data, to both of the users in the event that the document data are stored in the box and, also, for erasing the access authority, which has been granted to the user, when the user logs out. Thus, in the event that the user stores the data such as document data or the like in the box other than his or her personal box, the user can be permitted to make access to the data, while the owner of such box is warranted a high security and conveniences of data management are ensured.