A user inputs an ID and password, using an operating panel. When a start key is pressed to instruct the start of copying of a document, a dot pattern detection unit detects, from image data, a dot pattern formed according to a predetermined period. When a dot pattern is detected, a display control unit causes an operating panel to display a message indicating that a dot pattern has been detected. When the continuation of a copying operation is instructed, then after the completion of reading of the document, the image log generation unit generates an image log and log information and image log transmit ion control unit transmits the image log and log information to a computer of an administrator.