PURPOSE: To obtain mesophase of raw material of carbon material in high yield, by holding heavy oil under reduced pressure at specific range of temperature and viscosity, generating mesophase at high concentration in a short time and making easy to take-out from reaction vessel in hot state.

CONSTITUTION: Heavy oil such as coal tar, petroleum-based asphalt or ethylene bottom oil is heated at 300W550°C and held under reduced pressure (usually ≤300mmHg is preferable) at the point of time of 10W1×107 poise viscosity, thus mesophase is grown, solidified and foamed. Next, the mesophase is crushed (preferably 10W40μm) in hot state in non-oxidative atmosphere and taken out from reaction vessel. The mesophase obtained by such process is able to be molded without using of binder such as phenolic resin or pitch and the molded material is carbonized at a thousand and hundreds degree, then subjected to graphitization at two thousands and hundreds degree to produce a carbon material.