To provide a diffracting optical element which can relieve the decrease in diffraction efficiency due to angle dependency, can suppress the generation of flare light by light of unnecessary order and has high diffraction efficiency in a wide wavelength region and an optical system which has the diffracting optical element.

The diffracting optical element has a 1st diffracting optical element and a 2nd diffracting optical element arranged closely to each other and is in the power arrangement wherein the 1st and 2nd diffracting optical elements has mutually reverse power and the 1st diffracting optical element decreases the angle of incidence of some prescribed light beam on the 2nd diffracting optical element.