To provide an easy-to-manufacture secondary battery, which comprises spiral electrode plate group with less internal short-circuiting caused by fallout of an active substance on a side edge of the spiral center and breaking through a separator.

In the secondary battery composed of the spiral electrode plates being wound around a positive electrode plate and a negative electrode plate via a separator, the electrode plate thickness of the side edge of the center of the winding of at least either electrode plate is tapered down toward the tip.