Abstract: Disclosed are a five-membered heterocyclic compound polymer substantially constituted of repeat units represented by the following general formula: ##STR1## and a process for preparing the five-membered heterocyclic compound polymer described above by electrolytic oxidation of a monomer represented by the following formula in the presence of a supporting electrolyte and a solvent: ##STR2## The five-membered heterocyclic compound polymer of the present invention is high in electric conductivity and stable in the air. This polymer is, therefore, utilized for electronic materials, display materials and coating materials for electric conductive substances.