Abstract: An optical data recording/reproducing device including a light source adapted to project a laser beam containing s-polarized light as a major component along with a minor proportion of p-polarized light, a polarizing beam splitter located in a light path of said laser beam for mainly transmitting p-polarized light and reflecting off s-polarized light, an APC photosensor element located in a position for receiving transmitted p-polarized light from said polarizing beam splitter for detection of light intensity, and a data recording and reproducing photosensor element located in a position for receiving return light of s-polarized light reflected off toward an optical disc surface by said polarizing beam splitter.