Polarizing diffraction element and optical head device

A polarizing diffraction element having a wavelength selectivity which functions as a polarizing diffraction element at a wavelength lambda1, and which does not function as a diffraction grating not depending on incident polarization state and shows high transmittance at a wavelength lambda2, and an optical head device employing the element, are provided. The polarizing diffraction element selectively diffracts or transmits incident light having two different wavelengths each containing a first circularly polarized light and a second circularly polarized light having a rotation opposite from the rotation of the first circularly polarized light, depending on wavelength and polarization state of the incident light. Then, a reflective wavelength region for at least the first circularly incident light, does not contain said two incident wavelengths.