A single plate type optical unit and display device to utilize light with high efficiency in a simple method is configured so a dichroic mirror separates light into a plurality of colors, and the plurality of colors of light reflected by the dichroic mirror are beamed onto a rotating multisurface element, the plurality of colors of light emitted from the rotating multisurface element are each beamed onto different locations on the display element, and by rotating the rotating multisurface element, the plurality of colors of light are moved in one direction along the display element, and a color image is beamed from a projection lens.