NOVELTY - A photochemical electrode (101a) has a layer (101) containing aluminum-gallium nitride (I), gallium nitride layer (102), gallium oxide layer (103) and electrode layer (104) laminated on its surface from a light irradiation surface side.    USE - Photochemical electrode is used as anode electrode in anode cell of device used for reducing carbon dioxide into methane, ethylene, methanol, ethanol, isopropanol, allyl alcohol, acetaldehyde, propionaldehyde, formic acid and carbon monoxide (all claimed).    ADVANTAGE - The photochemical electrode improves reduction efficiency of carbon dioxide. The amount of reduction products obtained from carbon dioxide is improved.    DETAILED DESCRIPTION - A photochemical electrode has a layer containing aluminum-gallium nitride of formula: AlxGa1-xN (I) (where x is more than 0 and 0.25 or less), gallium nitride layer, gallium oxide layer and electrode layer laminated on its surface from a light irradiation surface side. INDEPENDENT CLAIMS are included for the following:    (1) carbon dioxide reducing device, which comprises a cathode cell for accommodating the primary electrolyte solution containing carbon dioxide, anode cell for accommodating secondary electrolyte solution, and a proton-permeable film interposed between the cathode cell and the anode cell. A cathode electrode is installed inside the cathode cell, such that cathode electrode is in contact with the primary electrolyte solution and contains a metal or a metallic compound on the surface. An anode electrode is installed inside the anode cell, such that anode electrode is in contact with secondary electrolyte solution. The cathode electrode and the anode electrode are electrically connected not through the external power supply; and    (2) reduction of carbon dioxide, which involves preparing carbon dioxide reducing device, and reducing carbon dioxide in primary electrolyte solution of cathode electrode by irradiating light having wavelength absorbable in the aluminum-gallium nitride layer of anode electrode.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of basic structure of the photochemical electrode.    Layer containing aluminum-gallium nitride (101)    Anode electrode (101a)    Gallium nitride layer (102)    Gallium oxide layer (103)    Electrode layer (104)