Abstract: An image forming apparatus of the present invention is provided with elements for use in image formation as expendable supplies; with a detachable replacement unit 108 having a movement 205 which can move from a first position to a second position but which once it moves to the second position, is prohibited from returning to the first position, having a moving member that serves to move the movement 205 from the first position to the second position, and having a drive mechanism that causes the moving member to move the movement 205 in conjunction with the drive of the elements; with a sensor 703 which detects a position of the movement 205; and with a controller which judges whether the replacement unit 108 is a new one or not on the basis of the result of detection of the sensor 703 anterior and posterior to the drive of the drive mechanism.