A laser oscillator is provided that makes it possible to stably obtain a laser beam output in continuous or pulsed oscillation that has an intensity distribution of a top-hat profile or a fundamental transverse mode profile. The assembly comprises a bifurcated inflation shaft defining a shaft inner lumen, a first balloon defining a first balloon lumen, and a second balloon defining a second balloon lumen. The elongated support is attached to a first and second bracket. In addition, since the spring compression mechanism and so on can be attached to the valve element driving part without any alternation of the valve element driving part, the spring compression mechanism can be shared by two or more motor-operated valves, and reduction of expense for a diagnosis of a motor-operated valve and improvement in accuracy of diagnosis can be achieved.