Provided is an optical scanning apparatus, including: a deflector which deflects light beams with first and second deflection surfaces to scan first and second scanned surfaces in a main scanning direction; first and second imaging optical systems which guide the deflected light beams to the first and second scanned surfaces; and an incident optical system which allows the light beam to obliquely enter the first deflection surface in a sub-scanning section, in which the first imaging optical system includes a first optical element having an absolute value of curvature radius of incident surface smaller than an absolute value of curvature radius of exit surface in the sub-scanning section including an optical axis, and the incident surface of the first optical element reflects the light beam entering the incident surface toward a direction of separating from a main scanning section including the deflector in the sub-scanning section including the optical axis.