An electrode group for a battery including a positive electrode and a negative electrode wound into a spiral with a separator interposed therebetween, wherein the positive electrode includes a positive electrode current collector and positive electrode material mixture layers formed on both sides of the positive electrode current collector, the negative electrode includes a negative electrode current collector and negative electrode material mixture layers formed on both sides of the negative electrode current collector, a lead is connected to at least one of the positive electrode current collector and the negative electrode current collector, and at least one of step portions having difference in level formed in the electrode group by lengthwise ends of the positive electrode, the negative electrode and the separator and the periphery of the lead, respectively, is covered with an insulating member arranged on an inner circumference side or an outer circumference side of a turn of the electrode group.