A positive electrode and a negative electrode include stress relaxation regions each of which includes a tab and a lead of each electrode and may include a region divided by a slit provided for the electrode. In the case where the stress relaxation region includes a tab and a lead, the length of the stress relaxation region is 20% or more and 50% or less of the sum of the lengths of the lead and the electrode not overlapping with the lead in an inner region of a secondary battery. In the case where the stress relaxation region further includes a region divided by the slit, the length of the stress relaxation region is 20% or more and 95% or less of the sum of the lengths of the lead and the electrode not overlapping with the lead in an inner region of a secondary battery.