To densely wind to increase capacity density per volume and make size small by winding a positive electrode plate and a negative electrode plate through a separator, making the diameter larger than the height in the winding axis direction, and forming in a flat shape.

A positive electrode plate and a negative electrode plate 4 each formed by applying an active material to a current collector are cylindrically wound through a separator 2 to produce a power generating element jellyroll 5. The jellyroll 5 is formed in a flat cylindrical shape whose height 5a is smaller than the diameter 5b. The jellyroll 5 can densely be wound without concentrating the pressure on a part, capacity density per volume can be increased, expansion in charging is made in the vertical direction to the axis, the surface 15 in the vertical direction resists expansion pressure, and use of thin material is made possible. The jellyroll 5 is housed in a flat container of a square pillar type 13 or a cylindrical type 16 to form a battery, the battery is made easy to handle, and effectively utilized even in small electronic equipment.