A positive electrode 14 has a positive electrode current collector 11 on which positive electrode mixture layers 12a, 12b are formed. A negative electrode 24 has a negative electrode current collector 21 on which negative electrode mixture layers 22a, 22b are formed.
The positive electrode 14 and the negative electrode 24 are wound into a flat shape with a separator 31 interposed therebetween, thereby an electrode group 4. In a curved portion located at an end portion in a major axis direction of the electrode group 4, at least one of the positive electrode 14 or the negative electrode 24 is provided with uncoated portions 13a, 13b; 23a, 23b in which the mixture layers 12a, 12b; 22a, 22b are not formed on the current collector 11;21.