Recent trends in laser application systems such as optical information systems, optical network systems, and optical measurement systems have increased the need for small size, light weight, low cost, and mass producibility. Advantages of a micro grating device in laser application systems are high integration capability, design flexibility, and mass producibility. In particular, several approaches have been presented for the application of micro grating devices to optical heads for CD players. However, few studies have been made to apply to MO disk heads. This is because it is difficult to realize polarization separation. In this paper, we propose a grating beam splitting polarizer based on form birefringence, which has several applications to MO disk heads including polarization separation, optical path separation, and signal detections. The polarization separation characteristics as a basic operation of the grating beam splitting polarization have been confirmed. The resultant extinction ratios obtained were -7 dB for the ordinary light and -6 dB for extraordinary light.