The optical scanning apparatus includes a polygonal rotatable mirror which deflects a light beam emitted from a light source, a drive motor which rotates said polygonal rotatable mirror, and an optical box which holds said drive motor, wherein a fitting hole in which a bearing of said drive motor fits, is provided in said optical box, and a wall surface of this fitting hole has notch portions partially arranged. Thereby, the heat release property of the bearing of the polygonal rotatable mirror drive motor becomes good.