By using a winding type electrode plate assembly resistant to displacement by wind-up and buckling, a lithium ion secondary battery, capable of suppressing deterioration in cycle and storage characteristic caused by expansion and shrinkage of the electrode plate due to charge/discharge cycles or by generation of gas during storage at high temperatures or the like, is accomplished. An electrode plate A comprising a binder mainly composed of a polymer material "a" and an electrode plate B, having the opposite polarity to the electrode plate A, with a porous polymer layer mainly composed of the polymer material "a" or a copolymer of the polymer material "a" formed thereon, are wound up in flat form to give a flat electrode plate assembly, which is soaked in a non-aqueous electrolyte and then heated and cooled, with the soaked state maintained, while pressure is applied in the direction of the thickness of the flat electrode plate assembly, to integrate the electrode plate assembly.