To provide a polarized light lighting optical system which has high efficiency of use of light from a lamp.

The polarized light lighting optical system comprises a light source unit projecting light having a random polarizing direction, an optical means operating as a lens as specified, and a polarized light separating prism means, and is characterized in self-feedback type polarized light lighting arrangement wherein P-polarized light is projected from a polarized light separating prism to become illumination light and S-polarized light is separated and reflected to return to a lamp side and then reflected by a metal mirror etc., in the lamp to be converted into P-polarized light to be projected from the lamp again.