PURPOSE: To make a gas flow between electrodes uniform and make discharge uniform, by forming planar supporting members with which both bases for supporting facing electrodes are linked, making the members parallel with the gas flow between both bases, and arranging a plurality of the members in the perpendicular direction with respect to the direction of the gas flow in a separated pattern.

CONSTITUTION: In an excimer laser oscillating apparatus, supporting members 19 with which two bases 3 and 4 for supporting facing electrodes ER are linked are formed with electric conductors, and the supporting members 19 serve the role of a charging and discharging wiring part A. In this apparatus, said supporting members 19 are made to be planar shapes and are made parallel with the direction of gas flow between both bases 3 and 4. A plurality of the members are arranged in the perpendicular direction with respect to the direction of the gas flow in a separated pattern. In this constitution, the planar supporting members 19 which serve the role of the charging and discharging wiring A do not hinder the gas flow through a main discharging part 1. Conversely, the gas flow can be straightened. Therefore, the gas flow from a fan 6 which is disturbed with a heat exchanger 7 is corrected with the supporting members 19. The gas flow between the electrodes is made uniform, and the discharge can be made uniform.