A prismatic secondary battery includes a flat electrode assembly including one end having stacked positive electrode substrate exposed portions and including the other end having stacked negative electrode substrate exposed portions, and includes a positive electrode collector and a negative electrode collector connected to the corresponding outermost surface in the stacking direction of the stacked positive electrode substrate exposed portions and the stacked negative electrode substrate exposed portions, respectively, by resistance welding; the positive electrode substrate and the negative electrode substrate have thicknesses different from each other; a rib of the positive electrode collector and a rib of the negative electrode collector have heights different from each other; and each leading end in the height direction of the ribs has approximately the same height.