An ultraviolet laser apparatus having a single-wavelength oscillating laser generating laser light between an infrared band and a visible band, an optical amplifier for amplifying the laser light, and a wavelength converting portion converting the amplified laser light into ultraviolet light using a non-linear optical crystal. An exposure apparatus transfers a pattern image of a mask onto a substrate and includes a light source having a laser apparatus emitting laser light having a single wavelength, a first fiber optical amplifier for amplifying the laser light, a light dividing device for dividing or branching the amplified laser light into plural lights, and second fiber optical amplifiers for amplifying the plural divided or branched lights, respectively, and a transmission optical system for transmitting the laser light emitted from the light source to the exposure apparatus.