To provide a production technique suitable for mass-producing fullerene nanowhisker/nanofiber nanotubes.

Disclosed is a method for producing a metal-supporting carbon, which comprises supporting a metal microparticle on the surface of carbon black in a thin fluid layer by a liquid phase reduction process, wherein the thin fluid layer is formed between a pair of treatment planes which are arranged opposed to each other in such a manner that the planes are movable close to and apart from each other and at least one of the planes can rotate relative to the other one. Also disclosed is a method for producing a crystal composed of a fullerene molecule and a fullerene nanowhisker/nanofiber nanotube, which is characterized by agitating and mixing a solution comprising a first solvent having fullerene dissolved therein with a second solvent in which fullerene has lower solubility that in the first solvent in a thin fluid layer homogeneously, wherein the thin fluid layer is formed between a pair of treatment planes which are arranged opposed to each other in such a manner that the planes are movable close to and apart from each other and at least one of the planes can rotate relative to the other one.