Provided is an optical system in which chromatic aberrations can be excellently corrected in spite of environmental changes, to thereby maintain high optical performance. The optical system includes: a plurality of optical elements each having refractive surfaces located in a light incident side and a light exit side; and an aperture stop. A focal length, an Abbe number of a material, and an extraordinary partial dispersion ratio of each of an l-th optical element and an r-th optical element which satisfy a condition related to the extraordinary partial dispersion ratio are suitably set.