A battery production method according to the invention includes a winding step of winding an electrode assembly around a winding core and a flattening step of pressing the electrode assembly wound in the winding step, in a direction orthogonal to an axial direction thereof to form a flattened shape in which the wound electrode assembly is flattened in a direction that is orthogonal to the pressing direction and the axial direction, wherein a rod-shaped spacer is inserted, in parallel to the axial direction, into the electrode assembly wound during the course of winding the electrode assembly around the winding core in the winding step, and wherein the spacer is pulled out between the winding step and the flattening step.