PURPOSE: To carry out proper treatment according to factors, such as purity, shape and number of materials to be treated, and enhance economical efficiency and reliability of the treatment by carrying out the treatment based on specific treating conditions in a method for treating a carbonaceous material at a high temperature while passing a highly purifying gas therethrough.

CONSTITUTION: A carbonaceous material is highly purified by a method for highly purifying treatment of the carbonaceous material at ≥2000°C temperature while passing a highly purifying gas composed of a halogen gas and/or a halogen compound therethrough. In the aforementioned method, the treatment is carried out under treating conditions determined by formula 1 based on analytical results of the reaction rate for removing impurities with the highly purifying gas. In formula 1, t is the shortest required treating time (min); A is the target impurity content (ppm); AO is the impurity content (ppm); kmn is the reaction rate constant (1/min); CAS is the highly purifying gas concentration (%); C'AS is the highly purifying gas concentration (%) in analyzing the reaction rate; n is the order of the reaction; Ef is the catalyst effectiveness factor.