Abstract: An optical head of the present invention applicable to an optical disk drive includes a light-transmitting phase shifting device. The phase shifting device reduces aberration ascribable to a difference in the thickness of the substrate of an optical disk. This not only insures the effective reproduction of data out of optical disks having different substrate thicknesses, but also guarantees a sufficient quantity of light representative of a reproduced signal and a sufficient lens numerical aperture. The optical head therefore achieves a desirable reproduced signal characteristic.