To obtain a diffraction element in which the diffraction efficiency is controllable in such a way that the dependance of the diffraction efficiency upon wavelength is substantially constant or in another way, and to provide an optical head device having a high degree of freedom of designing and a high light utility efficiency by mounting the diffraction element on the optical head device.

The diffraction element is provided with a periodical rugged portion formed on a transparent substrate 3, the projected portions have different refractive indices and is provided with an optical multilayer 1 arranged in parallel with the transparent substrate and at least the recessed portions are filled with a packing material 2 which has refractive index different from that of the transparent substrate, and the diffraction element is mounted in an optical path located between a light source of the optical head device and an objective lens.