A method of selectively removing carbonaceous impurities from carbon nanotubes (CNTs). In an example method, impurities formed on the surface of the CNTs may be removed by a sulfidation reaction between the impurities and sulfur in a sealed space. More specifically, a method of selectively removing only amorphous carbon by which carbon nanotube walls do not react with sulfur and only carbonaceous impurities formed on the surface of the CNTs make sulfidation reaction (C+2S.fwdarw.CS.sub.2), that is, a method of selectively removing carbonaceous impurities from the CNTs integrated in a device by sulfidation is provided.