PURPOSE: To reduce the leakage of a welded part and improve the strength of a sealed vessel by a method wherein holes, opening at the clearance between a stator and a rotor, are arranged on a frame and a gap gauge is enabled to fit into the clearance by penetrating through a compressing element.

CONSTITUTION: The sealed vessel is consisting of an upper part 11 and a bottom part 12, which are formed by deep drawing, and the stator 5a is forcibly fitted into and secured to the inner wall of the upper part 11 while a cylinder 14, a bearing 15, a rotary shaft 16 and the rotor 5b are incorporated into the frame 13 which is inserted into the inner wall of the upper part 11 for the sealed vessel. The frame 13 is provided with the holes 13a at four places located at positions whereat the holes are opening at the clearance 5c between the stator 5a and the rotor 5b while the frame 13 is secured to the upper inner wall of the sealed vessel by welding 17 such as an arc spot or the like under fitting the gap gauge 6 into the clearance 5c after penetrating through the holes 13a. Lastly, the gap gauge 6 is pulled out and the sealed vessel section 12 is capped for welding.