PURPOSE: To realize the economical reuse of waste paper in a simple and easy way and to obtain the title material improved in adsorptivity by carbonizing waste paper in an atmosphere extremely deficient in oxygen in a hermetically sealed oven to give a material having specified carbon content, inner surface area and apparent specific gravity.

CONSTITUTION: A double-walled carbonization oven having a hermetically sealed carbonization chamber 13 provided in a heating chamber 12 is charged with waste paper 30, such as old newspapers, magazines, books, various documents or paper used for office automation appliances through a charge part 13b into the carbonization chamber 13, and fuel material 40 comprising, e.g. a waste material is fed around the chamber 13 so as to provide a quantity ratio of the waste paper 30 to the fuel material 40 of 1:(5 to 10). The waste paper is then carbonized by heating at 300°C or higher, preferably 700-800°C, for 5-6hr in an atmosphere extremely deficient in oxygen to give a carbonaceous material having a carbon content of 80-85%, an inner surface area of 150-200m2/g and an apparent specific gravity of 0.05 to 0.30.