An optical scanning apparatus includes a deflector configured to deflect a light beam from a light source to cause the light beam to scan a surface to be scanned in a main scanning direction, an incident optical system that includes a single incident optical element and is configured to guide the light beam from the light source to the deflector, and an image-forming optical system configured to condense the light beam having been deflected by the deflector as condensing points on the surface to be scanned. At least one of the incident optical system and the image-forming optical system includes a diffractive surface that corrects displacement amounts of the condensing points in a main scanning section and a sub scanning section when a wavelength of the light beam from the light source varies.