Electrochemical reduction of carbon dioxide using a gas-electrolysis cell reactor was studied. A new electrocatalyst has been screened and Co-phthalocyanine (Co-Pc) supported on carbon support was found to reduce CO2 to CO. Effects of reaction conditions on a formation rate of CO and a selectivity to CO corresponding to a current efficiency (CE) were studied. Loadings of Co-Pc, kinds of carbon materials as a support, reaction temperatures and cathode potentials strongly affected the performance of the electroreduction of CO2 to CO. A maximum CE to CO formation was achieved to 70% with 14 mA cm -2 by use of 0.1 wt% Co-Pc supported vapor-grown-carbon-fiber (VGCF) electrocatalyst at -0.90 V (Ag/AgCl) and 273 K. The reaction model of electroreduction of CO2 was proposed in this work.