Abstract: An optical scanning apparatus includes: a light source for emitting a laser light ray; a cylinder lens for converting the laser light ray into a first convergent light ray that converges only in a sub-scanning direction and remains unchanged in a main scanning direction; a deflection unit for deflecting the first convergent light ray from the cylinder lens; a focusing unit for converting the deflected light ray into a second convergent light ray that converges in the main scanning direction, and for focusing the second convergent light ray on a scanned surface as a light spot; an aperture unit, arranged between the light source and the deflection unit, for blocking an outer peripheral portion of the laser light ray and for restricting a width of the laser light ray in the sub-scanning direction to a first width of an aperture of the aperture unit; and an adjusting unit for adjusting the first width of the aperture of the aperture unit so as to eliminate a deviation of the diameter of the light spot on the sca