Patent ID: 8883260

Claim:
A carbon nanotube producing method comprising: preparing a base having a catalyst layer, and disposing the base in a synthesis furnace; blowing an oxygen-free, carbon compound-containing feedstock gas from a feedstock gas supply pipe toward the catalyst layer provided on the base over a surface of the base; forming a heating region in the synthesis furnace by heating the feedstock gas supplied into the synthesis furnace through a blow hole of the feedstock gas supply pipe; adjusting a residence time of the feedstock gas so as to increase by increasing a heat volume, wherein the heat volume is a volume of a channel for the feedstock gas supplied into the heating region so as to come into contact with the catalyst layer on the base; and evacuating the feedstock gas out of the synthesis furnace, wherein said adjusting of the residence time comprises arranging the catalyst layer and the blow hole such that the blow hole is provided opposite a surface of the catalyst layer, and such that the distance between the surface of the catalyst layer and the blow hole is 40 mm or more, and wherein the residence time is adjusted to be in a range of 4 seconds to 30 seconds.