An image forming apparatus includes a unit, which is detachably attachable to a main body of the apparatus and has a portion to be detected, and a detecting device which detects the portion to be detected in the unit. It is determined that the unit is in an unused state since both of a first state in which the portion to be detected is detected by the detecting device and a second state in which the portion to be detected is not detected by the detecting device are confirmed, and thereafter, the first state or the second state is maintained. Furthermore, there is provided a restricting member which inhibits the first state or the second state from being maintained.