PURPOSE: To obtain pitch for producing carbon fiber of high modulus type having high strength, by bringing a pitch material before treatment with a hydrogen donor solvent and reduced pitch after the treatment into contact with an alkali, and then with an acis, followed by polymerizing the pitch thermally.

CONSTITUTION: A pitch material before it is treated with a hydrogen donor solvent such as tetrahydroquinone, etc. and/or reduced pitch after the treatment is brough tinto contact with an alkali [preferable example; alkaline(earth) metal hydroxide, ammonia, etc.], and, then, with an acid (preferably example; oxalic acid, or nitric acid). Then, as low-boiling components are removed by reduced pressure method, etc., the pitch is thermally polymerized at 400W500°C, to give the aimed pitch.

USE: A reinforcing material for resins, metals, etc.