The invention relates to a multi-room diaphragm electrolysis method and device for electroreduction of carbon dioxide into carbon monoxide, and belongs to the technical field of carbon dioxide resource utilization. According to the multi-room diaphragm electrolysis method and device, an electrolytic tank is divided into a plurality of electrode rooms through a perfluoro sulfonated ion exchange membrane, and a multi-room diaphragm electrolytic tank with alternately-arranged cathode rooms and anode rooms is formed; a cathode electrolyte is an organic composite electrolyte dissolved with the carbon dioxide, and an anode electrolyte is a water solution containing a supporting electrolyte; a cathode is a metal electrode having high selectivity on carbon monoxide making through electrolysis of the carbon dioxide, and an anode is a noble electrode; and in the electrolytic reaction process, water has an oxidizing reaction with the anode to generate oxygen, the carbon dioxide has a reduction reaction with the cathode to generate the carbon monoxide. By means of the multi-room diaphragm electrolysis method and device, electroreduction of the carbon dioxide into the carbon monoxide can be efficiently and continuously carried out.