This invention relates to a carbon nanotube producing system. A carbon nanotube producing system includes a reaction tube in which a metal catalyst and a carbon-containing gas are supplied and carbon nanotube grows on the metal catalyst by pyrolysis; an exhaust line along which a gas including the carbon nanotube grown on the metal catalyst is exhausted from the reaction tube; and a carbon nanotube trapping apparatus installed on the exhaust line and configured to trap the carbon nanotube grown on the metal catalyst by using a magnetic force.