To provide a projection type display device using a light valve, which ensures improved contract of a projection image.

A ray of light from a light source is separated into a ray of red light, a ray of green light, and a ray of blue light by a color separation optical system. The separate rays of color light are passed through their respective polarizers, enter a polarization beam splitter, are polarized and separated by a polarization-separation section and emitted to a reflection type light valve. The rays of light reflected and emitted after modulated by the reflection type light valve re-enter the polarization beam splitter, are polarized and separated by the polarization-separation section and then detected. A polarizer is disposed in the optical path of at least one of the detected rays of color light. The ray of color light passed through the polarizer and the other rays of color light enter a color composing optical system in order to be subjected to color composition, and then projected by a projection lens.