An ink circulation apparatus, comprising: an ink tank that accumulates radical polymerization-type UV-curing ink so as to be in contact with gas including at least oxygen, the ink tank being exposed to the atmosphere; a supplying flow path that communicates with the ink tank and a supply port of an inkjet head including the supply port to which the radical polymerization-type UV-curing ink is supplied, a nozzle that ejects the radical polymerization-type UV-curing ink, and a discharge port from which the radical polymerization-type UV-curing ink that is not ejected from the nozzle is discharged; a supply pump that is provided in the supplying flow path, and supplies the radical polymerization-type UV-curing ink accumulated in the ink tank to the inkjet head; oxygen removing means that is provided in the supplying flow path, and removes oxygen from the radical polymerization-type UV-curing ink; a discharging flow path that communicates with the discharge port of the inkjet head and the ink tank; a collecting pump that is provided in the discharging flow path, and collects the radical polymerization-type UV-curing ink discharged from the discharge port to the ink tank; and control means that changes mode between a first mode of removing oxygen from the radical polymerization-type UV-curing ink by the oxygen removing means and a second mode of not removing oxygen from the radical polymerization-type UV-curing ink, and to change a mode from the first mode to the second mode before electric power of the apparatus is cut off an ink tank that accumulates radical polymerization-type UV-curing ink so as to be in contact with gas including at least oxygen, the ink tank being exposed to the atmosphere; a supplying flow path that communicates with the ink tank and a supply port of an inkjet head including the supply port to which the radical polymerization-type UV-curing ink is supplied, a nozzle that ejects the radical polymerization-type UV-curing ink, and a discharge port from which the radical polymerization-type UV-curing ink that is not ejected from the nozzle is discharged; a supply pump that is provided in the supplying flow path, and supplies the radical polymerization-type UV-curing ink accumulated in the ink tank to the inkjet head; the supply port to which the radical polymerization-type UV-curing ink is supplied, a nozzle that ejects the radical polymerization-type UV-curing ink, and a discharge port from which the radical polymerization-type UV-curing ink that is not ejected from the nozzle is discharged; a supply pump that is provided in the supplying flow path, and supplies the radical polymerization-type UV-curing ink accumulated in the ink tank to the inkjet head; oxygen removing means that is provided in the supplying flow path, and removes oxygen from the radical polymerization-type UV-curing ink; a discharging flow path that communicates with the discharge port of the inkjet head and the ink tank; a collecting pump that is provided in the discharging flow path, and collects the radical polymerization-type UV-curing ink discharged from the discharge port to the ink tank; and control means that changes mode between a first mode of removing oxygen from the radical polymerization-type UV-curing ink by the oxygen removing means and a second mode of not removing oxygen from the radical polymerization-type UV-curing ink, and to change a mode from the first mode to the second mode before electric power of the apparatus is cut off