To manufacture a high-quality active carbonized material excellent in adsorption ability from organic sludge, and to adsorb and remove organic compound vapor in exhaust gas by using the active carbonized material.

The active carbonized material excellent in ability to adsorb organic compound vapor and having a bimodal pore structure is manufactured by treating a carbonized material, obtained by carbonization treatment or carbonization-activation treatment of organic sludge, with an acid having 0.1 N concentration to remove ash contained in the carbonized material. Organic compound vapor in exhaust gas is adsorbed and removed by passing the exhaust gas containing the organic compound vapor through an adsorption tower packed with the active carbonized material.