PURPOSE: To obtain a pitch high in its mesophase content, suitable for carbon fiber in high productivity, by separating heavy oil pitch intomesophase component and isotropic one taking advantage of specific gravity difference between them followed by removing residual isotropic pitch from the mesophase one by specified means.

CONSTITUTION: First, a heavy oil (pref. with high aromatic hydrocarbon content, such as a residual oil produced by catalytic decomposition of petroleum fraction) is heat-treated to separate the pitch formed into mesophase pitch and isotropic one taking advantage of specific gravity difference between them. Next, said mesophase pitch is brought into contact with a solvent of a solubility constant 8.5W12.5(cal/cc)1/2 (e.g. toluene) to eliminate the isotropic pitch left in the mesophase one, thus obtaining the objective pitch. Said heavy oil as the raw material is preferably one with the ash contained having been eliminated beforehand along with the light oil fraction by vacuum distillation.

EFFECT: Capable of giving carbon fiber with excellent spinnability and elastic modulus.