The heat generated by a laser oscillator is partly radiated toward a frame. The radiated heat is partly absorbed by a cooling mechanism. The remaining heat is transferred through a chamber which dissipates part of the heat, to a heat insulating panel, which blocks most of the heat. The heat generated by the laser oscillator is partly radiated outwardly and reflected by a casing inwardly toward the frame. The reflected heat is partly absorbed by cooling mechanisms. The remaining heat is transferred through chambers which dissipate part of the heat, to the heat insulating panel, which blocks most of the heat. Therefore, any temperature rise of the frame due to the heat generated by the laser oscillator is very small, and the frame is prevented from being deformed due to the heat from the laser oscillator. Because the frame is not deformed, a laser beam emitted from the laser oscillator is applied to a desired position which remains unchanged.
