PURPOSE: To provide the light beam separating element which is small in size and has the high positional accuracy between plural light beam separating layers and the accuracy of facial angles by laminating and disposing plural pieces of the light beam separating layers by holding transparent substrates at a prescribed angle with the incident surface of light beams.

CONSTITUTION: The light beam separating layer 31 which is multilayered films of metallic thin films or dielectric thin films is formed on one surface of the transparent substrate 32 which is flat and is exactly controlled in thickness. For example, a quartz glass is used as the transparent substrate 32. ZrO2 of a high refractive index and MgF2 of a low refractive index are used in order to execute polarized light sepn. as the light beam separating layer 31. Plural pieces of the substrates 32 formed with the light beam separating layers 31 are laminated and the substrate 33 not formed with the light beam separating layer is laminated on the uppermost layer. These substrates are adhered with a refractive index matching transparent adhesive. The laminate is then cut out at the faces 34 to 37 of the suitable angle, for example, 45° with the light beam separating layers 31 and the cut out surfaces are polished to be flat.