The method for reducing carbon dioxide of the present invention includes a step (a) and a step (b) as follows. A step (a) of preparing an electrochemical cell. The electrochemical cell comprises a working electrode (21), a counter electrode (23) and a vessel (28). The vessel (28) stores an electrolytic solution (27). The working electrode (21) contains boron carbide. The electrolytic solution (27) contains carbon dioxide. The working electrode (21) and the counter electrode (23) are in contact with the electrolytic solution (27). A step (b) of applying a negative voltage and a positive voltage to the working electrode and the counter electrode, respectively, to reduce the carbon dioxide.