A positive electrode (11) according to one embodiment is provided with: a positive electrode collector (30); a first middle layer (32) disposed on one of two surfaces of the positive electrode collector (30), the surface being on the inner circumferential side when the positive electrode collector (30) is wound; a second middle layer (34) that is disposed on the other surface that is on the outer circumferential side; and a positive electrode mixed material layer (36) disposed on the first middle layer (32) and on the second middle layer (34). The first middle layer (32) and the second middle layer (34) contain insulating particles and an electrical conductor, and the thickness of the first middle layer (32) is less than the thickness of the second middle layer (34).