An optical pickup of a compatible type which can be switched for a DVD and a CD by a completely electrical control without the need of a mechanical moving device or the like and is suitable for the reduction in size and also has an excellent efficiency in the use of light. A liquid crystal panel of a transmission type which gives a phase difference of a 1/4 wavelength or a wavelength that is an odd number multiple of 1/4 wavelength to a transmission light and has a transparent electrode having an aperture pattern of a predetermined shape is used and the liquid crystal panel is arranged so that its plane of polarization crosses a plane of polarization of a polarization beam splitter at a predetermined angle. An applied voltage to the transparent electrode is controlled so that the whole surface of the liquid crystal panel functions as a 1/4 wavelength plate during a reproduction operation or a recording operation of the DVD and only the aperture pattern portion functions as a 1/4 wavelength plate during the reproduction operation of the CD.