A X-Y plane is a plane parallel to abutting surfaces on which a joining portion is formed, and a Z direction is a direction perpendicular to the X-Y plane. A sealing member is held between the outer circumference side of a guide provided on a lid body and the inner circumference side of a rib provided on a case, and is pressed in a direction parallel to the X-Y plane. Laser light is scanned on the inner circumference side with respect to a ring-shaped pressurization jig with a stopper pressurized by the pressurization jig, so the pressurization jig does not break the path of the laser light. This expands the range of options in the material for the pressurization jig, which enables an easy-maintenance jig to be used, improving productivity.