NOVELTY - A two-layer carbon nanotube is formed by contacting alcohol with metal catalyst held on a support at 600-950degreesC. The support has specific surface area 300 m2/g or more and has at least one or more peaks in region of 1-10 nm of pore diameter in pore distribution measurement by nitrogen absorption process. The change rate of peak intensity of support before and after baking in air at 800degreesC is 5% or less, according to X-ray diffraction.    USE - For manufacturing two-layer carbon nanotube used for electron-emission material (claimed) for field emission display and solar cell. Also used for cathode material of lithium secondary battery and fuel cell, electromagnetic shielding material, material for probe of scanning tunneling microscope, and nano pincette.    ADVANTAGE - The method efficiently provides two-layer carbon nanotube having thin diameter. The two-layer carbon nanotube has excellent field-electron-emission ability.    DETAILED DESCRIPTION - An alcohol is contacted with a metal catalyst held on a support at 600-950degreesC, to obtain carbon nanotube having two-layer carbon nanotube as essential component. The support has specific surface area 300 m2/g or more according to nitrogen absorption process, and has at least one or more peaks in region of 1-10 nm of pore diameter in pore distribution measurement by nitrogen absorption process. The change rate of peak intensity of the support before and after baking in air at 800degreesC is 5% or less, according to X-ray diffraction.    INDEPENDENT CLAIMS are included for the following:    (1) two-layer carbon nanotube-containing composition. 80 or more of 100 carbon nanotubes in the composition are two-layer carbon nanotubes, when arbitrarily selected by transmission electron microscope (TEM). The average distance between bending portion in two-layer carbon nanotube selected by TEM, is 100 nm or more. The ratio of maximum peak intensity in 1560-1600 cm-1 with respect to maximum peak intensity in 1310-1350 cm-1 of two-layer carbon nanotube, is 10 or more according to resonance Raman-scattering measurement. The metal content of the composition is 1 wt.% or less, according to elemental analysis; and    (2) electron-emission material containing two-layer carbon nanotube-containing composition.    DESCRIPTION OF DRAWING(S) - The figure shows the pore-volume distribution curve of mesoporous material and borosilicate used as support material. (Drawing includes non-English language text).