At least one exemplary embodiment is directed to a telephoto type optical system capable of reliably correcting and/or reducing aberrations such as chromatic aberration. The optical system includes a refractive optical element which includes a solid-state material, a negative lens component and a positive lens component, respectively disposed on a front side relative to a pupil, the solid-state material meeting conditions of an Abbe number .nu.d(GNL) and of a partial dispersion ratio .theta.gF(GNL) as follows: -2.100.times.10.sup.-3.nu.d(GNL)+0.693<.theta.gF(GNL) 0.555<.theta.gF(GNL)<0.9Then, a refractive power of the refractive optical element, a mean partial dispersion ratio of a material of the negative lens component, and a mean Abbe number of a material of the positive lens component are properly set.