The present invention relates to a method for producing a polymer/conductive carbon composite electrode comprising dehydration condensation polymerization of a tetramine derivative and a tetracarbonyl compound in the presence of an electrically conductive carbon material. The synthetized polymer comprises quinoxaline structural units such as polyphenyl quinoxaline (PPQ) and serves as an active material having proton conductivity. The composite material for electrode obtained by the method has a large capacity of inserting/releasing a proton and excellent in durability. An electrode comprising the composite material and a secondary battery comprising the electrode is excellent in safety and reliability high-speed current characteristics, has a longer life and a larger gravimetric energy density (Wh/kg).