The invention provides a nonaqueous electrolyte secondary battery having a cathode and an anode arranged so as to be opposite to each other, and an electrolyte layer put therebetween; wherein the cathode comprises: (a) a conductive polymer and (b) at least one selected from the group consisting of a polycarboxylic acid and a metal salt thereof, and wherein the anode comprises a material into which a base metal or ions thereof can be inserted and from which a base metal or ions thereof can be extracted. The invention further provides a cathode sheet for use in the nonaqueous electrolyte secondary battery mentioned above.