Each user can use an image forming system by performing authentication through an ID card. In a case where a first user does not remove an original even though reading of the original has finished, a user ID of the first user is stored. Next, when a second user removes the original, the user ID of the second user is stored associated with the user ID of the first user. The user ID of the first user who forgot the original and the user ID of the second user who removed this original are outputted, and therefore the first user can more easily discover the original by inquiring to the second user of the whereabouts of the original.