A hologram color filter diffraction-separates an incident lightwave using a hologram to project thus separated lightwaves having different-wavelengths at intended positions with a specified spatial period. The hologram color filter comprises a light-transmitting substrate (21) and a light-transmitting diamond-like-carbon (DLC) film (22) formed on the substrate. In the DLC film, a relatively-low-refractive-index belt-shaped region (n.sub.1, 22a) and a relatively-high-refractive-index belt-shaped region (n.sub.2, 22b) are placed alternately.