A secondary battery 1 includes a conductive member 130 that is provided in the secondary battery 1, and a current interrupt device 105 that is provided in the secondary battery 1 and has a reversal plate 120 that is welded to the conductive member 130. The conductive member 130 and the reversal plate 120 have thicknesses of T1 and T2, respectively, in the part in which the conductive member 130 and the reversal plate 120 are opposed to and in contact with each other, and the thicknesses T1 and T2 satisfy the relationship T1/T2