PURPOSE: To simplify and miniaturize the device by constituting a polarization beam splitter for polarizing and splitting a laser beam and an anamorphic prism for shaping the laser beam of an oval shape into a round shape with one member.

CONSTITUTION: The laser beam is emitted from a laser diode 2 in an optical head for recording and reproducing information recorded on a recording medium 1. The laser beam is shaped into an approximately oval shape by a wedge- shaped prism 11 consisting of a birefringent material provided in an optical path of the laser beam. Then, only a P-polarization component of the beam is made to be incident upon an objective lens 7, so as to allow an S-polarized component to come out of the objective lens 7, thus improving a quenching ratio.