Disclosed herein is a battery that includes a chargeable/dischargeable battery cell and an outer case that houses the battery cell. The outer case having first and second top plates overlapping each other as viewed in a thickness direction thereof. The first top plate has a first convex part and a first concave part having mutually different heights in the thickness direction, the second top plate has a second convex part and a second concave part having mutually different heights in the thickness direction. The first convex part overlaps the second concave part as viewed in the thickness direction, and the second convex part overlaps the first concave part as viewed in the thickness direction.