A secondary battery including an electrode body that includes a positive electrode plate and a negative electrode plate, an outer body that houses the electrode body, a metal sealing plate that seals an opening of the outer body, a positive electrode collector electrically connected to the positive electrode plate and the sealing plate, a negative electrode external terminal connected to the negative electrode plate through a negative electrode collector. In the secondary battery, a first projection and a second projection are formed on a surface of the sealing plate on a battery inner side, the positive electrode collector includes a first opening and a cut-out, the first projection is disposed in the first opening, the first projection and an edge portion of the first opening is welded and connected to each other, and the second projection is disposed in the cut-out.