The image forming apparatus detects a predetermined image data included in image data and transmits an electromagnetic signal to a memory card within a predetermined vicinity of the image forming apparatus. The memory card is configured to carried by a user of the image forming apparatus. The image forming apparatus receives identification information of the user from the memory card and has a memory which stores predetermined function information. The predetermined function information is associated with to the identification information of a predetermined user and defines functions of the image forming apparatus which the predetermined user is authorized to use. When the predetermined image data is detected by the detector, the image forming apparatus restricts the functions of the image forming apparatus based on the predetermined function information associated with the identification information of the predetermined user.