A method is presented for effectively manufacturing multi-wall
(double-wall, etc.) carbon nanotubes (CNTs) having a structure whereby
interior tubes are formed within the CNTs. In this manufacturing method,
fullerene/CNT hybrid structures are prepared, wherein assembled
fullerenes, these being fullerenes that are linked, have been housed
within single-wall CNTs. The interior tubes are formed from the assembled
fullerenes by subjecting the hybrid structures to electron beam
irradiation while in a heated state. It is preferred that irradiation
with the electron beams occurs at a temperature of 100.about.500.degree.
C. and with the electron beams having an accelerating voltage of
80.about.250 kV. According to the manufacturing method of the present
invention, multi-wall CNTs with few defects can be manufactured at lower
temperatures and in a shorter period than in the case where the
fullerene/CNT hybrid structures are only maintained under high
temperature conditions (and electron beam irradiation is not performed).