A secondary battery, comprising: a positive electrode; a negative electrode; a battery case housing the positive electrode and the negative electrode; a positive electrode lead electrically connected to the positive electrode; and an electrical insulating tape covering a part of the positive electrode lead, wherein the positive electrode has a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode current collector has, at a longitudinally central part of the positive electrode active material layer on the positive electrode current collector, an exposed part on which no positive electrode active material layer is formed, the positive electrode lead has a first end part connected to the exposed part and an extension part extending from the first end part toward an outside of a peripheral part of the positive electrode current collector, an electrical insulating layer is disposed on an outer surface of the first end part of the positive electrode lead, the electrical insulating layer is covered with the electrical insulating tape, and the electrical insulating tape covers a boundary part between the exposed part and the positive electrode active material layer, characterized in that the insulating tape has a larger width than that of the electrically insulating layer as measured in the longitudinal direction of the positive electrode, and in that the insulating tape includes a substrate layer containing an organic material and an adhesive layer adhering to the electrical insulating layer and the exposed part. a positive electrode; a negative electrode; a battery case housing the positive electrode and the negative electrode; a positive electrode lead electrically connected to the positive electrode; and an electrical insulating tape covering a part of the positive electrode lead, wherein the positive electrode has a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, the positive electrode current collector has, at a longitudinally central part of the positive electrode active material layer on the positive electrode current collector, an exposed part on which no positive electrode active material layer is formed, the positive electrode lead has a first end part connected to the exposed part and an extension part extending from the first end part toward an outside of a peripheral part of the positive electrode current collector, an electrical insulating layer is disposed on an outer surface of the first end part of the positive electrode lead, the electrical insulating layer is covered with the electrical insulating tape, and the electrical insulating tape covers a boundary part between the exposed part and the positive electrode active material layer, characterized in that the insulating tape has a larger width than that of the electrically insulating layer as measured in the longitudinal direction of the positive electrode, and in that the insulating tape includes a substrate layer containing an organic material and an adhesive layer adhering to the electrical insulating layer and the exposed part.