A carbon dioxide electrolytic device in an embodiment includes: an electrochemical reaction cell including: a first accommodation part that accommodates gas or a first electrolytic solution containing CO 2 ; a second accommodation part that accommodates a second electrolytic solution containing H 2 O; a diaphragm provided between the first and second accommodation parts; a cathode that is in contact with the gas or the first electrolytic solution; and an anode that is in contact with the second electrolytic solution; a first supply part that supplies the gas or the first electrolytic solution to the first accommodation part; a second supply part that supplies the second electrolytic solution to the second accommodation part; and a carbon dioxide separation part that is connected to a discharge portion of a discharge containing O 2 and CO 2 from the second accommodation part and includes a cryogenic separation device to separate CO 2 from a gas component in the discharge.