PURPOSE:To obtain the compact and high power CO2 laser device, by overlapping an AC soundless discharge on a conventional DC glow discharge, and keeping the uniform and stable discharge at the gas pressure of 50-100 Torrs. CONSTITUTION:Electrodes 10a and 10b on which Al is evaporated are formed on the outer wall of a glass tube 3. A high voltage AC11 is applied between electrodes 10a and 10b, and the soundless discharge is generated in the direction which makes a right angle with the DC discharge between the electrodes 6 and 7. If the gas pressure is increased only in the case DC discharge is made, the glow dischage is concentrated in the central axis of a laser tube 3, the laser output is decreased, and at last the oscillation is stopped. But by overlapping the soundless discharge having the spread in the direction of the diameter of the tube, the DC discharge is diffused, and the uniformly spread DC discharge can be maintained. Thus the operating pressure can be increased to 50-100 Torrs, the configuration of the laser device can be made small, and the output can be made large.