Described herein is a method of preparing nano-carbon; a method of preparing an electron emitting source by supporting the soot; and an apparatus for preparing the same. A torch electrode 10 of an arc torch 1 as a first electrode is placed opposite to a material to be arced 2 using graphite as a second electrode. A voltage is applied between the torch electrode 10 and an edge portion of the material to be arced 2 to generate are discharge, to evaporate the edge portion of the material to be arced 2 exposed to the arc discharge, to generate soot. The soot thus generated is deposited on the surface of a substrate opposite to an arc discharge-generating area through a mask having a patterned opening.