The present invention provides an optical head apparatus having: a light source emitting a linearly-polarized light; an objective lens focusing a light source light emitted from the light source on an optical recording medium; a light detector receiving a return light generated by reflecting the light source light by the optical recording medium; and a variable diffraction device having: a first polarized light diffraction grating; and a second polarized light diffraction grating, the variable diffraction device: diffracting an incident light of the linearly-polarized light by one of the first polarized light diffraction grating and the second polarized light diffraction grating; and transmitting the incident light without diffraction by the other thereof, the first polarized light diffraction grating having: first stripes including an anisotropic transparent material; and second stripes including an isotropic transparent material, the first stripes and the second stripes being alternately arranged in a first direction and in a first pitch to fill each space; the second polarized light diffraction grating having: third stripes including an anisotropic transparent material; and fourth stripes including an isotropic transparent material, the third stripes and the fourth stripes being alternately arranged in a second direction and in a second pitch to fill each space; the first polarized light diffraction grating and the second polarized light diffraction grating being different in at least one of the pitches and the directions, the variable diffraction device being capable of switching: either the first polarized light diffraction grating or the second polarized light diffraction grating diffracting the incident light; and the other thereof transmitting the incident light without diffraction by changing refractive indices sensed by the incident light with respect to the first polarized light diffraction grating and the second polarized light diffraction grating by an externally applied electric signal.