PURPOSE: To make the ratio of the internal volume to the entire volume of a thin battery large, increase the electric-discharge capacity of the battery, and prevent any liquid leakage of the battery by fixing an annular caulking part, which protrudes from the inner wall of a can coated with an insulating film, to the can by pressing and tightening the annular caulking part.

CONSTITUTION: The entire surface of a can 8 made of a metallic member is coated with a fluorine-system film 8a. The lower opening part of the can 8 is attached around a positive terminal 7 made of a metallic member. A negative terminal 9 made of a metallic member has an external-terminal touching part 9a in its upper part, and an annular caulking part 9b in its lower part. The negative terminal 9 is integrated from outside the can 8 into the upper opening hole 8b of the can 8, and fixed to the can 8 by pressing and tigtening the annular caulking part 9b protruding inside the can 8. A separator 13 separates a positive active material 11 and a negative active material 12, which is impregnated with electrolyte, from one another so as to prevent any electric short- circuit. By the means mentioned above, the ratio of the internal volume to the entire volume of the battery is made large, the electric-discharge capacity is increased, and any liquid leakage can be prevented.