An optical scanning apparatus, including: a light source unit; a deflection unit; an incident optical system; and an imaging optical system, wherein at least one optical surface of a plurality of imaging lenses included in an imaging optical system has a non-circular shape in a sub-scanning section perpendicular to a main scanning direction, and a non-circular amount of the non-circular shape changes along the main scanning direction, and wherein the followings are satisfied: ds(Y=0) 0, where ds(Y=0) and ds(Y=Ymax) respectively represent a paraxial field curvature at a center position in a sub-scanning direction perpendicular to the main scanning direction and a paraxial field curvature in the sub-scanning direction at a maximum image height in an effective scanning range of the surface to be scanned by the beam from the light source unit in the main scanning direction, among field curvatures at a center position in the effective scanning range.