To provide a manufacturing method of a battery or a capacitor, in which a status of an isolation la that is deteriorated due to a damage it receives can be grasped on its way of manufacturing, and which can contribute to a quality improvement.

A battery or a capacitor is manufactured by assembling an isolation layer 9 and a positive electrode 1 and a negative electrode 5. A marking 9x for determination of a deterioration such as a convection pattern is given, and the isolation layer 9 in which a polymer is used as a base material is prepared. A contacting operation, in which, a liquid matter M, in which a monomer is a major component, and the isolation layer 9 come in contact, and an irradiation operation, in which an irradiation energy W for facilitating a polymerization is irradiated to the isolation layer 9, are performed to facilitate the polymerization in the isolation layer 9. After at least either the contacting operation or the irradiation operation, the deterioration status of the marking 9x for the determination of the deterioration is checked, and the deterioration status of the isolation layer 9 is checked by the checking means 19, 22.