Provided is a lithium ion secondary battery that enables lithium ion replenishment in a short period of time. The lithium ion secondary battery disclosed herein is provided with a wound electrode assembly in which a long sheet-shaped positive electrode and a long sheet-shaped negative electrode are wound such that the negative electrode is positioned on the outer side of the positive electrode; a third electrode that is disposed outside the wound electrode assembly and that has an Li supply source capable of supplying lithium ion; and a porous insulating film that is disposed between the wound electrode assembly and the third electrode and that is formed from a material usable as a separator in a battery. In this lithium ion secondary battery, the third electrode has a portion facing, across the insulating film, an outer surface of the negative electrode that constitutes the outermost circumference of the negative electrode of the wound electrode assembly, and has a portion facing, across the insulating film, a wound electrode assembly open end face that communicates with the interior of the wound electrode assembly and is an end face of the wound electrode assembly along the direction of the winding axis.