Upon the combination of double refraction and diffraction effects, a new kind of polarization device is proposed, which is made of the birefringent plate with the grooves of a sawtooth profile on its surface. This device may separate an incident light beam into two polarized beams spatially with a high extinction ratio and large beam‐splitting angle, moreover it has a sheet form, large aperture, and low cost, thus being suitable for practical use. ©1995 American Institute of Physics.