Provided is a zoom optical system which includes, in order from an object, a first lens group having negative refractive power and other lens groups, and in which an interval between each lens group changes upon zooming, wherein the first lens group includes a first negative lens which is disposed closest to the object and has a diffractive optical element on an image side lens surface, and a positive lens disposed closer to the image than the first negative lens, and the glass material used for the positive lens satisfies the following conditions expressions: ν1p≦35 and Δ(θg, F)≧0.007, where ν1p denotes an Abbe number, based on the d-line, of the glass material used for the positive lens of the first lens group, and Δ(θg, F) denotes a deviation of the partial dispersion ratio of the glass material, which is used for the positive lens, from a standard line that connects a glass type A and a glass type B in a graph of which abscissa is an Abbe number νd based on the d-line, and the ordinate is the partial dispersion ratio (θg, F)=(ng−nF)/(nF−nC), with the Abbe number νd and the partial dispersion ratio (θg, F) of the glass type A and the glass type B being as follows: Glass type A: νd=60.49, (θg, F)=0.5436; glass type B: νd=36.26, (θg, F)=0.5828.