Secondary battery and method for manufacturing secondary battery

A method for manufacturing a secondary battery, comprising, when mutually intersecting three directions are assumed to be a first direction, a second direction, and a third direction, respectively,

• a winding step of superimposing a positive electrode sheet, a negative electrode sheet, and a separator and winding the positive electrode sheet, the negative electrode sheet, and the separator around a winding axis extending in the first direction, to prepare a wound electrode body, and
• a pressing step of pressing the wound electrode body in the second direction and also in the third direction to flatten the wound electrode body, to thereby form a first flat surface and a second flat surface facing each other with the winding axis interposed therebetween, and a third flat surface and a fourth flat surface disposed between the first flat surface and the second flat surface and facing each other with the winding axis interposed therebetween, on outer peripheral surfaces of the wound electrode body.