Abstract: Provided is a battery case which preferably corresponds to increases in size and thickness of the battery case. The battery case is made of metal provided with an explosion-proof valve. The explosion-proof valve is continuous with a plate part configuring the battery case. The explosion-proof valve includes a folded part formed by folding the plate part, a thin plate part which is continuous with the folded part and arranged inside the folded part, a thick plate part which is continuous with the thin plate part and formed thicker than the thin plate part in the middle of the explosion-proof valve, and a breaking groove which is arranged in the thin plate part and configured to rupture when a predetermined pressure is exerted thereon.