A battery includes an external terminal member and an insulating member on an outer surface of a lid member so that an interval between the insulating member and the lid member is smaller in a long side of the lid member than in a short side. A weld mark is formed over the entire circumference of the lid member to extend across the outer surface of the lid member and an open end face of the case body. The weld mark not only extends across the outer surface of the lid member and the open end face of the case body but also reaches an outer side surface of the case body in a zone of the long side of the lid member facing the insulating member, but does not reach the outer side surface of the case body in a zone except the former zone.