An image forming apparatus includes: a photosensitive member; a developing roller; a contact/separation mechanism configured to switch between a contact state in which the developing roller is brought into contact with the photosensitive member and a separation state in which the developing roller is separated from the photosensitive member; a photosensitive-member motor configured to rotate and drive the photosensitive member; and a control portion. The control portion configured to determine that the contact/separation mechanism is in a failure state in a case where a torque of the photosensitive-member motor is not detected to have changed by at least a predetermined value within a predetermined time after a predetermined reference timing.