A carbon dioxide enrichment device, comprising: first and second gas diffusion electrodes; and an electrolytic solution existing between them to be in contact with them, wherein the electrolytic solution contains solvent and solute dissolved in it, and the solute is dissolved to form a dissolved inorganic carbon containing carbonic acid, hydrogen carbonate ions, or carbonic acid ions; oxygen is consumed by an oxygen reduction reaction on the first gas diffusion electrode, whereby a dissolved inorganic carbon is formed by a dissolution and ionization reaction of carbon dioxide in the solvent; the dissolved inorganic carbon derived from the solute or the dissolved inorganic carbon is transported to the second gas diffusion electrode; and oxygen is formed from the solvent in the vicinity of the second gas diffusion electrode by an oxidation reaction of the solvent on it, and carbon dioxide is formed from the dissolved inorganic carbon.