A quarter wavelength plate for reducing the dependence of a retardation value on an incident beam angle in optically anisotropic crystals. The quarter wavelength plate is formed of optically anisotropic crystals in a thickness of 0.1 mm to 0.5 mm. The quarter wavelength plate can contribute to a reduction in the dependence of the retardation value on the angle at which a light beam impinges on the quarter wavelength plate, and to a reduction in color shading caused by a rise in temperature. A reflection type liquid crystal display device which employs the quarter wavelength plate can enhance the luminance and contrast.