The present invention provides a system for reducing and fixing carbon dioxide whereby carbon dioxide can be fixed in a gaseous state without supplying outside energy. This system (1) for reducing and fixing carbon dioxide is characterized by comprising a reactor (1A) having a cathode (11) and an anode (12) disposed with an electrolyte (13) therebetween, wherein electrons are generated by an oxidation reaction at the anode (12) while the gas-phase carbon dioxide is fixed by reduction reaction at the cathode (11), and the cations or anions are transported through the electrolyte (13) so as to correct the bias in the charge between the electrodes that accompanies the oxidation reaction or reduction reaction, and the oxidation reaction at the anode (12) is the reaction in which the onset potential of the oxidation reaction versus the normal hydrogen electrode (NHE) potential at the operating temperature is more negative than the onset potential of the carbon dioxide reduction reaction at the cathode (11) under t
