The analysis of the degradation mechanism of all-solid-state lithium polymer secondary batteries was carried out by using a combination of several electrochemical measurement methods. Although there have been few reports about the technique of identifying various resistances (electrolyte bulk, anode-electrolyte interface, cathode-electrolyte interface), it has become possible to quantitatively separate the resistances in the all-solid-state lithium polymer secondary battery. As a consequence, it was clarified that in the battery, the degradation of the LiCoO2 cathode-solid polymer electrolyte interface is dominant. (c) 2005 Elsevier B.V All rights reserved.