A lithium ion secondary battery having an electrode group that includes: a winding core, a positive electrode containing a positive electrode core member and a positive electrode active material layer, a negative electrode comprising a negative electrode core member and a negative electrode active material layer, and a porous film including a filler and a binder formed on at least one of the positive and negative electrodes which are wound around the winding core. The positive electrode and/or the negative electrode have/has, on the initial winding side, a region where the active material layer is carried on only one side of the core member and a region where the active material layer is carried on neither side of the core member, at a position closer to the initial winding position than the region where the active material layer is carried on only one side of the core member.