PURPOSE: To improve polarization contrast by letting conductor stripes have an almost rectangular or trapezoidal cross section and making the thickness of stripes almost equal with the mutual internal of these stripes.

CONSTITUTION: Concerning a polarizer having the pattern of parallel stripes 2, the pattern of parallel stripes 2 has predetermined width and predetermined mutual interval, and this pattern is prepared from an electrically conductive or non-transmissive material so as to form a diffraction grating having a predetermined space or diffraction grating cutting interval (g) (=width+gap). In this case, the stripes 2 have the rectangular or trapezoidal cross section and its thickness is equal with or thicker than the predetermined interval. Thus, polarization contrast can be increased.