This paper was made to investigate on production of gypsum hardened body contained active carbon (carbonized substance) by heating waste gypsum plaster board sprayed reducing agent solution in order to carbonize lining paper in gypsum board and its adsorption property of volatile organic compounds. The waste gypsum board sprayed 1 mol·dm-3 ZnCl2 solution or 70vol%H2SO4 was heated at 300-700°C for 1-60 minutes in the electric furnace. Then, the product was ground and gypsum body was produced by hydrating at water-carrying capacity of 100-200%. The products were characterized by means of X-ray diffraction, thermal analysis and specific surface area measurement. The specific surface area of active carbon reached to 250m2·g-1 by heating at 700°C for 4 minutes after spray of zinc chloride solution onto surface of waste gypsum board. The obtained active carbon had pore diameter of 4 nm. However, water of crystallization of gypsum decreased till about 2.5%. Amount of moisture absorption of prepared gypsum body was 4 times as compared with that of gypsum hardened body prepared from usual calcined gypsum. Also, amount of moisture absorption increased with the decrease of water-carrying capacity. On the other hand, HCHO adsorption ratio of gypsum body increased with the increase of water-carrying capacity. The HCHO adsorption ratio was improved by producing small gypsum hardened body.