To obtain an integrator element, an optical unit, and a display device, which each has simple constitution and good light use efficiency.

Provided are a source light converging means of converging the light from a light source on a specified position, and a light beam angle converting means, nearby the specified position, which is larger in area of its projection surface than of its incidence surface and converts projection light to have a maximum projection light beam angle smaller than the maximum incidence light beam angle of incident light. Optical waveguide light provided with the means is interposed between the light source and a video display element, which is irradiated with illumination light to project a color picture from a projection lens.