Grating element, optical pickup optical system and method of designing grating element

A method of producing a grating element including a plurality of diffraction members each having a protrusion and a recess arranged periodically on one surface of a transparent substrate, comprising:

• laminating the plurality of diffraction members in a substantially perpendicular direction to the transparent substrate;
• forming the protrusion of at least one diffraction member of the plurality of diffraction members by a dielectric multilayer film;
• and
• forming the dielectric multilayer film by laminating dielectric films of two or more types in the substantially perpendicular direction on the transparent substrate,
• wherein wavelengths of laser beams diffracted at predetermined diffraction efficiencies by the plurality of diffraction members are different from one another.