Provided is an illumination device that includes: light source (101); light guiding means (102) where light from light source (101) is supplied to one end surface, and light incident from the one end surface is propagated inside to exit from the other end surface; illuminating optical systems (103, 104, 106, and 107) that spatially separate a luminous flux output from the other end surface of light guiding means (102) into a plurality of luminous fluxes and that form, on display element (110), an optical image formed on the other end surface of light guiding means (102); reflective polarizing plate (109) that is located between illuminating optical systems (103, 104, 106, and 107) and display element (110) and that transmits first polarized light while reflecting second polarized light different in polarized state from the first polarized light toward illuminating optical systems (103, 104, 106, and 107); reflecting element (105) that is disposed at a position where the plurality of luminous fluxes are spatially separated and that reflects light reflected by reflective polarizing plate (109) toward reflective polarizing plate (109); and phase plate (108) located between reflecting element (105) and reflective polarizing plate (109). Reflecting element (105) includes a transmission region through which the plurality of luminous fluxes are transmitted, and a reflecting film formed in a region other than the transmission region.