An exposure device for producing semiconductors and liquid crystals has an optical system capable of effectively using light generated without making a hole in a lamp discharge vessel when high energy laser light is supplied to it for emitting light, such as ultraviolet light. The exposure device has a light source for emitting ultraviolet light, a laser device for emitting laser light, an elliptical reflector for reflecting ultraviolet light emitted from the light source, and an optical system for directing light reflected by the elliptical reflector to an article to be treated via optical elements including a collimator lens and an integrator lens, and a beam splitter having a wavelength selecting ability provided in the optical path for light reflected by the elliptical reflector to allow laser light to be incident on the light source from and opening side of the elliptical reflector.