A closed battery, according to the invention, comprises a substantially flat box-type outer case 60 having electrical conductivity, provided with an opening on one side in the longitudinal direction thereof and other peripheral sides that are closed, a spiral electrode body 21 housed in the outer case, comprising a positive electrode, a negative electrode, and a separator interposed therebetween, an electrode current collector tab 21a larger in thickness than a core body, welded to a cut and raised piece that is cut and raised from an exposed part of the core body of one of the electrodes of the spiral electrode body, and a sealing plate 50 for covering and sealing the opening of the outer case, wherein the outer case is sealed by laser-welding with the electrode current collector tab being clamped between the rim of the opening and the sealing plate when sealing the opening of the outer case.Under the construction described above, since the mechanical strength of the electrode current collector tab is enhanced, improvements in the performance and reliability of the closed battery can be obtained.