Abstract: A carbon dioxide gas laser oscillation apparatus having one or more discharge tubes each having a pair of anode and cathode electrodes at least one of which is non-grounded and one or more high voltage DC power sources each connected between the pair of electrodes of each discharge tube provides with one or more conductors each being arranged on each discharge tube in the vicinity of the non-grounded electrode of the pair of electrodes but on one side of the non-grounded electrode opposite to a space between the pair of electrodes. The CO.sub.2 gas laser oscillation apparatus further provides with one or more current detection circuit for detecting a current flowing between zero-potential terminal and ground terminal of the high voltage DC power source, thereby enabling to detect an abnormal discharge within each discharge tube.