A nonaqueous electrolyte secondary battery which can reliably perform a current cut-off operation in a current cut-off state and can release a gas in a cleavage state. In the nonaqueous electrolyte secondary battery, an electrode element is held in a circularly cylindrical outer packaging can. A lid, a PTC element, and a safety valve are caulked on one end side of the outer packaging can through a gasket to seal one end of the outer packaging can. At the central portion of the safety valve, a projecting portion projecting toward the electrode element is formed. The projecting portion is welded on a sub-disk welded on the free end of a positive electrode lead. In the safety valve, a plurality of linear thin portions are formed along two circles centering on the projecting portion. A thin portion extending in a radial direction is formed across the end portions of the thin portions adjacent to each other. In this manner, by the plurality of thin portions, one continuous thin portion is formed.