The optical scanning apparatus includes a deflecting unit that scans first and second (FaS) scanned surfaces in main scanning direction by deflecting FaS light fluxes incident on a first deflecting surface at different angles with respect to main scanning section in sub-scanning section, and a first optical element including FaS optical portions which guide FaS light fluxes deflected by deflecting unit to FaS scanned surfaces, respectively. An incident surface of first optical element projects most toward deflecting unit at a position of surface vertex on the incident surface in sub-scanning section including the surface vertex. At least one of FaS exit surfaces of FaS optical portions is a sagittal tilt surface. A distance between surface vertices on FaS exit surfaces in sub-scanning section including an incident position of axial ray is larger than the corresponding distance in sub-scanning section including an incident position of outermost off-axis ray.