As a means for increasing the yield of carbon nanotubes produced by gas-phase catalysis, provided is a production device for producing carbon nanotubes by gas-phase catalysis, the production device characterized by being provided with: a first chamber that has a growth region that is a region where carbon nanotubes are formed; a first temperature adjustment device that can adjust the temperature of the growth region inside the first chamber; a pressure adjustment device that can adjust the pressure inside the first chamber; a first supply device that can supply a carbon source to the growth region inside the first chamber; a second temperature adjustment device that can adjust the temperature of a solid-phase iron-group-element-containing material that is disposed inside the production device; and a second supply device that can supply a halogen-containing substance to the inside of the production device such that the iron-group-element-containing material that is adjusted to a prescribed temperature by the second temperature adjustment device can react with a gas-phase halogen-containing substance.