There is provided an image forming optical system in which, it is possible to achieve both, the small-sizing and slimming of an optical system, and a favorable correction of various aberrations, mainly the chromatic aberration.In an image forming optical system including a lens component in which, a shape of another optical surface C of an intermediate layer L2 which is made of a transparent material having Abbe's number νd2 which is in a close contact with one optical surface B of a lens L1 which is made of a transparent material having Abbe's number νd1, is an aspheric shape differing from (a shape of) the optical surface B, and furthermore, a lens L3 which is made of a transparent material having Abbe's number νd3 is in a close contact with the optical surface C, the following conditions are satisfied 0.012