To provide the photographic optical system which has high performance and is low-cost by using the diffraction optical element.

A 1st positive convex meniscus lens of which the object side is convexed, a lightness stop, and a 2nd biconvex positive lens are arranged in order from the object side and a diffraction surface is formed on the object side of the 1st lens. Thus, the lightness stop, at least two lenses, and at least one diffraction surface are provided and a condition 0<dDOE/f<0.24 is met, where (f) is the focal length of the whole system and dDOE is the distance from the lightness stop to the diffraction surface on the optical axis. This is a condition for making light beam height small by arranging the diffraction surface nearby the lightness stop so as to balance a power chromatic aberration.