A diffractive optical element (10) includes a substrate (11), a protective film (13a, 13b), and a diffraction grating (12a, 12b) disposed between the substrate (11) and the protective film (13a, 13b), wherein the diffraction grating (12a, 12b) is formed of a composite material containing a resin and inorganic particles, a volume ratio of the inorganic particles with respect to the composite material is equal to or smaller than 50% by volume, and the diffraction grating (12a, 12b) has a thickness of equal to or smaller than 20 μm. Since the diffractive optical element (10) uses the composite material containing the resin and the inorganic particles as a material for the diffraction grating (12a, 12b), which is relatively difficult to process, the moldability improves compared with the conventional case of using glass, etc.