A method of processing radioactive waste resin by pyrolyzing radioactive waste ion exchange resin generated in a nuclear plant such as a nuclear power station. First, the ion exchange resin is pyrolyzed at a low temperature, and the resulting decomposition gas is separated. Second, the ion exchange resin at a high temperature, and the resulting decomposition gas is separated. Finally, the residue of the ion exchange resin is hot-pressed into a molded article (50).