An R-light optical system 14, a G-light optical system 15, and a B-light optical system 16 are disposed correspondingly to an R-light LED chip 11, a G-light LED chip 12, and a B-light LED chip 13, which emit an red light (R light), a green light (G light), and a blue light (B light), respectively. The R-light optical system 14, the G-light optical system 15, and the B-light optical system 16 are formed by combining a reflecting plate, a refractive lens, and a diffraction grating appropriately. The R-light optical system 14, the G-light optical system 15, and the B-light optical system 16 distribute all of the R light, the G light, and the B light, which are diffused widely, toward a cross dichroic prism 17.