To provide a method and apparatus for treating a waste gas containing fluorine-containing compounds, according to which PFCs can be decomposed efficiently even at low temperature, and moreover fluorine from the product of the decomposition can be recovered for reuse efficiently. An embodiment of the present invention relates to a method of treating a gas containing a fluorine-containing compound, comprising contacting the gas with a treatment agent comprising a mixture of aluminum hydroxide and calcium hydroxide. Moreover, another embodiment of the present invention relates to an apparatus for treating a gas containing a fluorine-containing compound, comprising a treatment column comprising a hollow interior that is packed with a treatment agent comprising a mixture of aluminum hydroxide and calcium hydroxide and through which the gas can pass, heating means capable of heating the hollow interior to a prescribed temperature, a gas introduction port for introducing the gas to be treated into the hollow interior, and an exhaust pipe for discharging gas produced from the hollow interior.