Aimed at preventing a laser light beam profile from fluctuating, and by using the fact that there is a substantially proportional relation between the beam profile and the charging voltage as well as between the beam profile and the composition or the total pressure of the laser gases, an excimer laser device comprises a laser chamber containing laser gases which are excited by initiating an electric discharge in the laser chamber to output laser light, a beam profile detector for detecting a beam profile of the output laser light, and a controller for controlling a electric discharge voltage (excitation intensity) and composition or total pressure of the prescribed types of laser gases in such a way that the beam profile is shaped as desired based on detection results of the beam profile detector. An excimer laser feedback control circuit detects the output laser beam width and controls the beam width by controlling one or more of the laser voltage, composition of the laser gas, pressure or partial pressure of the laser gas, or feed rate of a laser gas. The laser gas may comprise a halogen, buffer, or rare gas.