PURPOSE: To prevent the generation of a crack in a melt-stuck glass by performing a welding providing a groove on a metallic flange between a welding part of a flange and a glass in case the glass melt-stuck metallic flange is mutually welded.

CONSTITUTION: In case the 1st glass 2 melt-stuck to the 1st metallic flange 1 and the 2nd glass 4 melt-stuck to the 2nd metallic flange 3 are welded at a welding part 5 of the metallic flanges 1, 3, a cut groove 6 is respectively provided on the flanges 1, 3 in advance between the welding part 5 and the glasses 2, 4. Then, the flanges 1, 3 on which the groove 6 is provided are welded at the welding part 5 and the thermal transmission to the glasses 2, 4 is restricted by the groove 6 and yet the thermal deformation of the flanges 1, 3 is softened. The generation of cracks in melt-stuck glass can thus be prevented.