An electrode active material layer containing an electrode active material and a binder. The binder is distributed in the electrode active material layer such that the amount of the binder increases continuously from an outer surface of the electrode active material layer toward the core. The amount of the binder present in the electrode active material layer per unit thickness is less than 10 in a region extending from a position 90% of the thickness of the electrode active material layer to a position 100% of the thickness of the electrode active material layer from a surface of the electrode active material layer facing the core, with 10 being assigned to the amount of the binder present in the electrode active material layer per unit thickness if the binder is uniformly distributed in the electrode active material layer.