To provide a light source device of a liquid crystal projector capable of efficiently achieving polarizing recycling with a simple constitution.

This light source device of the liquid crystal projector has a polarizing recycling lighting optical system 1 by an LED light source 20. The lighting optical system 1 has a mirror plane 41 formed of a reflection plane perpendicular to the optical axis 5 of the lighting optical system 1. A light emitting section 3 of the LED light source 20 is arranged at a position decentering from the optical axis 5 of the lighting optical system 1 on the mirror plane 41.