An image forming apparatus comprising: a main body; a process cartridge that is detachably mounted on the main body in a mounting/removing direction and that rotatably supports a photosensitive body about a rotational axis; a positioning guide ( 23R, 23L) that is configured to guide the rotational axis of the photosensitive body when the process cartridge is mounted on the main body, and to determine a position of the rotation axis of the photosensitive body with respect to the main body in a mounting state in which the process cartridge has been mounted on the main body; a photosensitive body drive gear that is configured to be capable of rotating in a forward and reverse direction and to transmit a rotational drive force to the photosensitive body in the mounting state; a regulating member that is configured to be in one of a lock state and an unlock state, in the lock state the regulating member prohibiting the rotational axis of the photosensitive body from moving in the mounting/removing direction, the rotational axis of the photosensitive body being released from the regulating member in the unlock state; a cover that opens and closes an opening formed in the main body, the opening allowing the process cartridge to be mounted on or removed from the main body; and a regulating member control unit that causes the regulating member to be in the lock state when the cover is closed and to be in the unlock state when the cover is opened, characterized in that the regulating member control unit comprises a rotation member having a cam portion, and a link member configured to rotate the rotation member in association with movement of the cover between an open position and a closed position, the rotation of the rotation member causing the cam portion to be rotated such that the regulating member is switched between the un lock state and the lock state. a main body; a process cartridge that is detachably mounted on the main body in a mounting/removing direction and that rotatably supports a photosensitive body about a rotational axis; a positioning guide ( 23R, 23L) that is configured to guide the rotational axis of the photosensitive body when the process cartridge is mounted on the main body, and to determine a position of the rotation axis of the photosensitive body with respect to the main body in a mounting state in which the process cartridge has been mounted on the main body; a photosensitive body drive gear that is configured to be capable of rotating in a forward and reverse direction and to transmit a rotational drive force to the photosensitive body in the mounting state; a regulating member that is configured to be in one of a lock state and an unlock state, in the lock state the regulating member prohibiting the rotational axis of the photosensitive body from moving in the mounting/removing direction, the rotational axis of the photosensitive body being released from the regulating member in the unlock state; a cover that opens and closes an opening formed in the main body, the opening allowing the process cartridge to be mounted on or removed from the main body; and a regulating member control unit that causes the regulating member to be in the lock state when the cover is closed and to be in the unlock state when the cover is opened, characterized in that the regulating member control unit comprises a rotation member having a cam portion, and a link member configured to rotate the rotation member in association with movement of the cover between an open position and a closed position, the rotation of the rotation member causing the cam portion to be rotated such that the regulating member is switched between the un lock state and the lock state.