A light scanning apparatus comprises a light source unit, a deflection unit, an incident optical system, and an imaging optical system including a transmission type imaging optical element and a reflection optical element are provided. A light beam deflected for scanning by the deflection unit passes through the imaging optical element in order of a first and a second transmission surfaces, and then passes through the imaging optical element again a third and fourth transmission surfaces. The first and fourth transmission surfaces of the imaging optical element are different in shape from another in the sub-scanning direction. Respective components are set so that, in a sub-scanning section, the light beam deflected for scanning is turned back by the reflection optical element and refracted/diffracted at the first transmission surface in a direction in which a reflected light beam passes through the third transmission surface, and that predetermined Conditional Expression is satisfied.