Preparation of Cu-solid polymer electrolyte (spe) composite electrodes for gas-phase electrochemical reduction of CO2 was studied by electroless plating methods. Among the combinations of plating solutions and reducing solutions used, the combination of Cu-Rochelle salt and 10% NaBH4 gave the most efficient spe electrode. With the electrodes made of cation-exchange (Nafion) and anion-exchange (Selemion) membranes as spe materials, the total current efficiencies for reduction products of CO2 had maximum values of 19 and 27%, respectively. The use of the former gave C2H4 as the major product, whereas, with the later, HCOOH and CO were obtained. From gas-phase electrolysis of the dummy exhausted gas from thermal-power plants, it was found that NO has no influence on the electroreduction of CO2, but the removal of SO2 is needed in order to obtain C2H4 in higher current densities. Furthermore CO2 in the exhausted gas is required to be concentrated up to more than ca. 30%.