Abstract: When preparing carbon fibers from mesophase pitches, we usually encounter to the formation of cracks along the fiber axis. The crack formation is the most serious and troublesome problem. A simple process which can effectively prevent the crack formation comprises preparing the carbon fibers from mesophase pitches by melt spinning sufficient only to give a rotatory motion to the molten mesophase pitches just before extrusion substantially around the axis of a spinning nozzle hole. The process employs a usual nozzle plate having a pitch introducing tube and a spinning nozzle hole further containing a plug member having an outer spiral groove such as a drill point or a worm gear which is inserted within the pitch introducing tube.