An industrially useful peroxo-carbonate is electrolytically produced using, as a raw material, carbon dioxide that is inexpensive and easily available. A process of producing a peroxo-carbonate, includes feeding a carbon dioxide gas into an electrolytic cell having a gas diffusion anode and a cathode, or feeding a liquid having a carbon dioxide gas dissolved therein into an electrolytic cell having an anode and a cathode, and electrolytically converting the carbon dioxide gas into a peroxo-carbonate. By properly setting up electrolytic conditions such as electrodes, a useful peroxo-carbonate can be produced with high current efficiency using inexpensive carbon dioxide as the raw material.