To suppress the generation of irregularity in an illuminance on an irradiating face, and a change of a polarizing state caused by influences of a stress double refraction inside a lens.

The lighting optical system which lights the irradiating face by a light from a light source includes: first fresnel lens faces (11a and 11b) and second fresnel lens faces (12a and 12b) arranged in an optical path. The lighting optical system is configured in such a way that a position of a step of the first fresnel lens faces is not overlapped with a position of a step of the second fresnel lens faces when viewing from an optical axis (AX) direction of the lighting optical system.