A metallic ring is insulatedly sealed around each of the positive electrode terminal and negative electrode terminal, previously, by the glass hermetic seal and ceramic hermetic seal in such a manner that it is sealed into the opening hole of the cover plate of a battery case. In this case, in order to prevent the corrosion of a metallic brazer which may occur in the ceramic hermetic seal and improve the workability, the ceramic material is brazed around the negative electrode terminal through a Au—Cu brazer or P—Cu brazer.