PURPOSE: To simplify operation by a user, to reduce the cost of a device, and to prolong the life of the device by setting an exposure part at an exposure feasible position interlocked with operation for attaching a photoreceptor unit.

CONSTITUTION: A lever 13 coupling a sliding or rotating mechanism, a photoreceptor positioning reference part 10 and an exposure part positioning reference part 12 is provided in the exposure part 1 positioned at the upper part of the photoreceptor unit 3. By transmitting and driving by the attaching/ detaching operation of the unit 3 so that the exposure part 1 is retreated from the attaching/detaching path of the unit 3, the unit 3 is attached/detached to the upper part. By retreating the exposure part 1 from the upper part of the unit 3, the unit 3 is easily taken out to the upper part without dividing the printing device into the upper and lower parts, and the time required for exchanging is shortened. The exposure part 1 is moved to be housed in the cover 11 in the printing device, and the exposure part 1 is protected from an external fault factor.