An exposure device in which a reticle having a circuit pattern of a semiconductor device formed on it is irradiated with light beam emanated from a light source, such as a laser light source, for exposing the circuit pattern formed on the reticle on a semiconductor wafer. The exposure device includes a light beam generator for illuminating the reticle having a semiconductor circuit pattern formed on it, an image-forming optical system for forming an image on a wafer of a light image produced on radiating a light beam on the reticle from the light beam generator. The exposure device also includes a movement unit for moving the wafer relative to the image-forming optical system, and an alignment unit for detecting the position on the wafer of the image formed on the wafer by the image-forming optical system for position matching the image by the image-forming optical system relative to the wafer. The light beam generator includes a light source for excitation, a first resonator and a second resonator. The first resonator is illuminated by the light beam from the light source for excitation and outputs the light beam from the light source for excitation after waveform conversion. The second resonator is illuminated by the light beam from the first resonator and outputs the light beam from the first resonator after waveform conversion.