An optical scanning system and an image forming apparatus having the same. The optical scanning system includes a light source, a deflector, an input optical system for directing a light beam from the light source to the deflector, and an imaging optical system for directing the light beam deflected by the deflector onto a surface to be scanned. The input optical system includes a first optical element having a power both in a main-scan sectional plane and in a sub-scan sectional plane, and a second optical element having a power in the sub-scan sectional plane. At least one surface of the first optical element has a shape being rotationally asymmetrical and, in the sub-scan sectional plane, being non-arcuate.