An insertion portion of a negative electrode terminal is inserted into through-holes provided in an outer insulating member, a sealing plate, an inner insulating member, and a terminal connection portion of a negative electrode collector, and the insertion portion is crimped. A countersunk hole is provided around the through-hole of the terminal connection portion. The insertion portion of the negative electrode terminal is radially expanded in the countersunk hole. A distal end of a thin portion provided at a distal end of the crimped part of the insertion portion and the edge of the countersunk hole are welded by application of a high energy beam, and a groove is provided on the outer peripheral side of the countersunk hole.