Method and apparatus for continuous production of carbon fibers

A method for producing carbon fibers using a vertical carbonizing furnace having a heating chamber therein, which comprises heating the chamber in such a manner that the temperature gradually increases from the upper end toward a lower end of the heating chamber, introducing a fiber to be carbonized from a fiber inlet provided at the upper end of the chamber, introducing an inert gas from a gas inlet provided at the lower end of the chamber to render the atmosphere in the chamber non-oxidizing, injecting an inert gas from at least one injection hole in at least one portion between the fiber inlet and the gas inlet to form a curtain of the inert gas across the heating chamber to prevent decomposition gases formed in the heating chamber to ascend, discharging the decomposition gases with the inert gas from at least one gas outlet each being provided at a lower portion of each inert gas injection portion, and recovering carbonized fiber from a fiber outlet provided at the lower portion of the heating chamber, wherein the heating chamber is heated to a temperature having an incline of from more than 300.degree. to not more than 950.degree. C. and wherein each of said gas outlets is provided at a position as close as possible to each injection hole.