A photographing optical system includes at least one of a positive lens and diffractive optical element being provided closer to an object side of the system than an intersection P of a light axis and paraxial chief ray, and a negative lens, provided closer to an image side than the intersection. The positive lens and the negative lens are formed of materials satisfying the following conditions when the maximum height of a paraxial marginal ray, passing through a lens surface, from the light axis at a location closer to the object side than the intersection is greater than a maximum height of the paraxial marginal ray, passing through a lens surface, from the light axis at a location closer to the image than the intersection: -0.0015 .times..nu.d +0.6425 <.theta.gF 60 <.nu.d where .nu.d is an Abbe number and .theta.gF is a partial dispersion ratio.