A method of forming carbon fibers at a low temperature below 450° C. using an organic-metal evaporation method is provided. The method includes: heating a substrate and maintaining the substrate at a temperature of 200 to 450° C. after loading the substrate into a reaction chamber; preparing an organic-metal compound containing Ni; forming an organic-metal compound vapor by vaporizing the organic-metal compound; and forming carbon fibers on the substrate by facilitating a chemical reaction between the organic-metal compound vapor and a reaction gas containing ozone in the reaction chamber.