PURPOSE: To satisfy fining of processing dimension, to improve use efficiency of a light amount of an exposure light source and to realize easiness of exposure amount control and compactness of a device.

CONSTITUTION: Fourth harmonic wave of basic wave of a laser medium is projected by continuous oscillation by an ultraviolet laser beam projection part 10, a light amount of projection light is controlled by a shutter 11 according to monitor result by an integrating light amount detection part 12 which monitors an integrating light amount of the projection light and a reticle 14 is irradiated with light wherein lowering of coherence and light strength distribution are made uniform by a coherence removal device 13A and a fly's eye lens 13B, respectively. A pattern of the reticle 14 is transcribed to resist applied onto a wafer 16 by performing exposure and irradiation for the exposure light source through a reduction projection lens 15.