A carbon nanotube which shows ferromagnetism without a ferromagnetic metal imparted thereto and also has high thermal stability is provided. The carbon nanotube is characterized by being doped with nitrogen (which differs from carbon in valence electron) such that the doped nitrogen is segregated in a strip form at one end of the carbon nanotube. The thus doped nitrogen causes the carbon nanotube to have a difference in electron density and to show ferromagnetism. The present invention makes it possible to provide a carbon nanotube showing ferromagnetism without the necessity of imparting any magnetic metal thereto.