A semiconductor wafer etching system exhausts an exhaust gas including fluorocarbon gas to an exhaust line. Two traps, that are capable of trapping the fluorocarbon gas in the exhaust gas by cooled adsorption and releasing the adsorbed fluorocarbon gas by heating, are alternately arranged on the exhaust line. The two traps are alternately separated from the exhaust gas and regenerated on a regeneration line which serves to release the adsorbed fluorocarbon gas from the traps. The trap which is in the trap mode to adsorb the fluorocarbon gas is cooled to −120° C. or less. The trap which is in the regeneration mode to release the adsorbed fluorocarbon gas is heated to −100° C. or more.