A laser oscillator capable of preventing contamination of optical
components by organic matter such as oil mist. Gas laser medium in an
optical resonator constituted by optical components is pumped by an
electric discharge generated in an electric discharge tube to produce a
laser beam. The gas medium flows at high speed in the electric discharge
tube incorporated in a circulating path including a blower. A part of
lubrication oil of the blower is evaporated and mixed into the gas
medium. Since the optical components are cooled by retaining mechanisms
to prevent temperature rise of the components and a gas stagnation occurs
between the optical component and the electric discharge tube, the
evaporated oil mist tends to be congealed and adhered to a surface of the
optical component. A photocatalyst arranged in the vicinity of the
optical component effectively decomposes and removes the oil mist.