An optical scanning device includes a first optical element that converts a cross-section shape of a light beam from a semiconductor laser to a desired shape; a second optical element that guides the light beam output from the first optical element to an optical deflector that deflects the light beam; and a third optical element that gathers the light beam deflected by the optical deflector onto a surface to be scanned to form a light spot thereby optically scanning the surface. At least one of the first optical element, the second optical element, and the third optical element includes a resin-made lens, at least one of the resin-made lenses has a power diffracting surface, and a surface shape of at least one of power diffracting surfaces is formed so that a power of a diffracting portion and a power of a refractive portion are cancelled out.