A method is disclosed whereby a functional nanomaterial such as a monolayer carbon nanotube, a monolayer boron nitride nanotube, a monolayer silicon carbide nanotube, a multilayer carbon nanotube with the number of layers controlled, a multilayer boron nitride nanotube with the number of layers controlled, a multilayer silicon carbide nanotube with the number of layers controlled, a metal containing fullerene, and a metal containing fullerene with the number of layers controlled is produced at a high yield. According to the method, when a multilayer carbon nanotube (3) is formed by a chemical vapor deposition or a liquid phase growth process, an endothermic reaction aid (H2S) is introduced in addition to a primary reactant (CH4, H2) in the process to form a monolayer carbon nanotube (4).