PURPOSE: To block the route allowing creep of electrolyte on the surface of a negative case essentialy, and increase the liquid-leakage resistant performance of a sealed battery by forming a metal layer, which electrically conducts with a conductive thermoplastic resin member, by plating on at least a part of the inner and the outer surfaces of the negative case.

CONSTITUTION: The side part of a positive case 7 is provided with an inwardly protruding annular concave part 7-a, which is used as a seat used for fixing a negative case 9, and a battery is sealed by inwardly curling the opening of the case 7. In such a battery, electrolyte is considered to have a possibility of leaking through the above sealing part on the positive electrode side as well as through the adjoining parts of two kinds of resins on the negative electrode side. However, on the positive electrode side, since there is a small creep of the electrolyte, a sufficient liquid-leakage performance can be achieved by a mechanical sealing as indicated in the figure. Besides, on the negative electrode side, since the adjoining parts of a sealing-plate main body 9-a and a conductive resin body 9-b are fused by thermal fusion, entrance of creep of the electrolyte is prevented by the fused area. Consequently, there is no possibility that the electrolyte leaks outside the battery.