Laser oscillator

A laser oscillator comprising:

• a cylindrical outer electrode;
• an inner electrode disposed concentrically with the outer electrode and forming a discharge chamber filled with a laser medium between the inner electrode and the outer electrode;
• a first resonator mirror provided on a first end side of the outer electrode and the inner electrode and configured to reflect laser light emitted from the discharge chamber,
• a second resonator mirror provided on a second end side of the outer electrode and the inner electrode and configured to reflect the laser light between the second resonator mirror and the first resonator mirror, and
• a support member configured to support the inner electrode,
• wherein the support member has an opening portion through which the laser light passes at a position corresponding to the discharge chamber, and at least a part of the opening portion has an opening width smaller than a beam diameter of the laser light emitted from the discharge chamber and serves as a space filter portion.