Provided are an optical element in which a thickness of a refractive optical portion having an extraordinary partial dispersion characteristic is suitably specified to minimize flare generated by a diffraction optical portion, to thereby sufficiently correct chromatic aberrations to obtain excellent optical performance, and an optical system including the optical element. The optical system includes a cemented portion in which the refractive optical portion made of a solid material and has a refractive action is brought into intimate contact with at least one of light incident and exiting surfaces of the diffraction optical portion having a plurality of diffraction gratings which are layered. An Abbe (νd), a partial dispersion ratio (θgF), and an extraordinary partial dispersion ratio (ΔθgF) of the solid material are suitably set.