To provide a projection type display device having high use efficiency of light which does not require a polarizer, in which the optical axe of incident light in an optical modulator coincides with that of light emitted from the optical modulator, and which h as little rise in temperature of an element due to absorption of light and little loss in light quantity of the incident and emitted light.

Three light sources, R, G and B, are provided, and after beams are made to pass through lenses 86, 87 and 88, the beams are formed into parallel beams by a dichroic prism 89, then are made incident on an optical modulator. The optical modulator consists of three kinds of optical modulation elements corresponding to R, G and B, respectively. Each optical modulation element is an interference modulation (IMOD) element in which a translucent fixed layer part is opposed to a translucent movable film through airspace.