To provide the light source unit for a reflection type polarizing and modulating element which can greatly be improved in light use rate and shortened in optical path length.

A 1st polarization beam splitter 4, a λ/2 wavelength plate 7, and a 2nd polarization beam splitter 5 generate S-polarized light beams L1s and L2s from the natural light beam L0 emitted by the light source part 3 of the light source device 10 for the reflection type polarizing and modulating element to lighten reflection type liquid crystal panels 1r, 1g, and 1b through a dichroic prism 2. Light beams which are polarized, modulated, and reflected by the liquid crystal panels 1r, 1g, and 1b are analyzed by the polarization beam splitters 4 and 5 and projected on a projection screen, etc., by a projection lens 6 to display a television video, etc.