PURPOSE: To perform fluorocarbon decomposition where the load of post treatment is reduced by irradiating the mixture consisting of a carbonaceous material and oxide or bases of alkaline earth metal with microwaves to make it get hot and bringing gaseous fluorocarbon into contact with the mixture in a hot state.

CONSTITUTION: A cartridge type reaction vessel 7 installed in an applicator 1 is irradiated with microwaves for an appropriate time, and gaseous fluorocarbon provided for treatment is fed into the reaction vessel 7 from one short pipe 4 side at an appropriate flow rate with a mixture 8 being get hot. In such a way, the gaseous fluorocarbon reacts with an oxide of alkaline earth metal in the mixture 8, which is decomposed into fluoride, chloride or their composites of alkaline earth metal and gaseous CO2. The gaseous CO2 is discharged from the other pipe 5 to outside the system, and the residual remains in the reaction vessel 7. Since the treatment is made in a batch step, when it is finished both ends of the reaction vessel 7 are closed by valves 9 and the reaction vessel 7 is removed from connectors 6.