A laser oscillator having a mechanism which makes it easy to correct distortion in the laser oscillator, and also has a simple structure. The laser oscillator has a housing located on an installation surface and a resonator held by the housing. The resonator has a total reflecting mirror, an outputting mirror, a discharge tube positioned between the mirrors, and a laser power source which injects excitation energy into the laser medium such as the carbon dioxide gas within the discharge tube. The resonator is held on the housing by means of a holding mechanism, such as a clamp, a bolt or a bearing. The laser oscillator has at least three nonextendable legs having a constant height, and at least one extendable leg having an adjustable height, so that the legs extend from a lower part of the housing.