An image forming apparatus includes an image bearing member for bearing a toner image, a transfer member for transferring the toner image from the image bearing member onto a sheet in contact with the image bearing member, and an openable unit including an openable member and a rotational shaft. In addition, a lock member locks the openable unit in a closed state by movement of the openable member, and a cam member, provided in the main assembly, rotatably moves the transfer member toward and away from the image bearing member. A force receiving portion, provided on the openable unit, receives a reaction force in contact with the cam member. The openable member includes the transfer member, and the cam member urges the force receiving portion when rotated to impart a force, for attracting the openable unit toward a locking direction by the lock member, to the openable member.