PROBLEM TO BE SOLVED: To exactly determine the removal state of VOC (volatile organic compounds) and reduce power consumption. SOLUTION: In the factory operating time zone, an exhaust gas containing VOC is introduced into a VOC treatment part 8, and the VOC is removed by absorption at an absorption removal part 24. In the factory operation closing time zone, an inlet-side damper 14 and an outlet-side damper 15 are fully closed. and a regeneration damper 16 is fully opened, and a regeneration blower 13 is operated. In addition, electric power is supplied to a metallic heater of a heating part 25, and the heated air is circulated through a circulation path in the direction of an inflow port pipe 9, the VOC treatment part 8, an outflow port pipe 11, a branched pipe 12 and the inflow port pipe 9 in that order. Consequently, an adsorbing material and a catalyst are heated, then the VOC is eliminated from the adsorbing material with the regeneration of the adsorbing material, and the catalyst is activated to accelerate the decomposition of the VOC. COPYRIGHT: (C)2009,JPO&INPIT