A novel electrochemical CO2 reduction system has been developed in which liquid CO2 was reduced electrochemically at a Cu electrode producing CO, CH4, C2H4, and HCOOCH3. We have succeeded in reducing CO2 with a current density of 420 mA/cm2 and a current efficiency of 85%; the former is higher than that used in industrial electrolyses such as in the chloralkali industry. The Tafel plots indicate that the supply of CO2 is no longer limited by its mass transfer.