Chlorine-containing waste is processed inside a heating device, an alkali metal compound and a calcium compound are given into the heating device while the temperature of a solid phase inside the heating device is maintained at 400 to 1500.degree. C., chlorine that is contained in the chlorine-containing waste and that has not been bound by the alkali metal compound is bound in the solid phase by the calcium compound, and chlorine is converted into alkali metal chloride from calcium chloride generated in the course of the processing of the chlorine-containing waste.