An optical scanning unit of an image forming apparatus may include: an optical housing configured to include at least one optical part and to have a light-beam emitting aperture through which a light beam can emanate from the optical housing; a shutter configured to cover the light-beam emitting aperture; and a driving unit configured to drive the shutter to and fro, thus opening and closing the light-beam emitting aperture. Such a driving unit further can operate to coordinate at least one of the opening and the closing to occur after activation and before deactivation of a writing operation conducted by the optical scanning unit, respectively.