Provided is an optical scanning unit including a light source configured to emit a laser beam, a deflector configured to deflect the laser beam, a lens through which the laser beam is to pass, and a frame housing the deflector and the lens. The frame includes a laser transmissive portion allowing transmission of the laser beam for emission of the laser beam outward from the optical scanning unit and an adjacent portion adjacent to the laser transmissive portion. The laser transmissive portion and the adjacent portion are integrally formed of resin. The laser transmissive portion and the adjacent portion alternatively each include identical resin.