A light beam polarization converter for converting non-polarized light beams of an illumination source into a single polarization state, which may be utilized in various electro-optical devices, such as liquid crystal projection type televisions. A polarization splitter film and a phase retardation film are utilized to make the incident light beams of a light source focused and refracted with an under plate. The light beam, upon passing through the under plate, goes through a series of optical processes of polarization splitting, reflection, total reflection and phase retardation, and subsequently becomes a light beam of a single polarization state output.