Disclosed is an optical scanning apparatus for repeatedly optically scanning a plurality of surfaces to be scanned, including: a plurality of light sources; an optical deflector for deflecting and reflecting a plurality of light beams emitted from the plurality of light sources; and at least one scanning optical system for guiding the plurality of light beams which are deflected and reflected by the optical deflector to the different surfaces to be scanned. In the optical scanning apparatus, the plurality of light beams incident on the optical deflector are incident on a deflection surface of the optical deflector at different angles to a normal of the deflection surface, the scanning optical system is commonly used for the plurality of light beams, and the scanning optical system includes a first optical element that satisfies 0.ltoreq.|.phi.1s|<0.001 where .phi.1s represents optical power of the scanning optical system within a sub scanning section.