A cylindrical secondary battery where safety can be secured even when an external pressure accompanying rapid deformation of the battery acts on the battery is provided in a battery having a large capacity. A lithium ion secondary battery has a capacity of 14 Ah, where an upper lid is fixed to a battery can which receives an electrode winding grope therein. The upper lid includes a diaphragm 2 formed with a rupturing valve and an upper lid cap whose peripheral edge portion is fixed to a peripheral edge portion of the diaphragm 2. The rupturing valve includes a rupturing groove 8 with a V-shaped section formed on a surface of the diaphragm 2 positioned on the side of the upper lid cap and a rupturing groove 18 with a U-shaped section formed on a surface of the diaphragm 2 positioned on the side of the electrode winding group so as to correspond to the position of the rupturing groove 8.