An image forming apparatus includes; a main body; a detachable member; a cover; a displacement member movable between a preventing position and a permitting position; a one-way link mechanism provided for displacing the displacement member from the preventing position to the permitting position when the cover is opened from a state in which the cover is closed and the displacement member is disposed in the preventing position, and for keeping the displacement member in the permitting position when the cover is closed from a state in which the cover is opened; a position detection unit for detecting a position of the displacement member right after a power supply unit has been switched on; and a history determination unit for determining an existence of a history showing an opening and closure of the cover while the power supply unit is left off based on the position of the displacement member.