The opening to be sealed in a battery is sealed with an electrical insulating sealant S by placing an electrical insulating sealing material C, including a first sealing material A that is soften by heat applied for sealing and a second sealing material B that is more difficult to soften by the heat applied for sealing than the first sealing material A, and by heating and successively cooling the electrical insulating sealing material C. The second sealing material B is in the form of a mesh. Thus, a sealed battery with few defectives such as a sealing failure and a short-circuit can be manufactured in a high yield rate.