Carbon nanotubes are grown by supplying raw material gas 30 comprising a carbon compound to be a raw material of the carbon nanotubes into the inside of a reaction vessel tube 14 in which a catalyst 26 to grow the carbon nanotubes is charged. At this time, halogen-containing material gas 32 to reduce the amount of a carbon product such as amorphous carbon produced besides carbon nanotubes that deposits on the surface of catalyst particles 44 due to supply of the raw material gas 30 is further supplied into the inside of the reaction vessel tube 14. Thereby, it is possible to produce elongated carbon nanotubes.