PURPOSE: To obtain a carbon fiber having high purity at a low cost by applying excimer laser beam to a gaseous mixture containing an organic compound as a carbon source and fine powder of a transition metal or an organic compound of a transition metal as a decomposition catalyst.

CONSTITUTION: A closed reactor 2 is charged with an organic compound (e.g. methane or benzene) as a carbon source from an organic compound container 5 and fine powder of a transition metal (e.g. iron or nickel) or an organic compound of a transition metal as a decomposition catalyst from a catalyst container 8 together with a carrier gas. An excimer laser beam generated by an excimer laser beam generator 1 is introduced to the reactor through a window of the reactor 2 to obtain the objective homogeneous fiber free from contaminants such as soot in high yield.