An objective is used in an optical pickup apparatus which conducts reproducing and/or recording information for three different types of optical information recording media each having different thickness protective substrate by using three different wavelength light fluxes respectively. The objective comprises a first diffractive structure and in which the diffraction order for the maximum diffraction efficiency is the same for all of light fluxes, and a second diffractive structure that diffracts the second light flux without diffracting the first and third light fluxes.