To provide a thermal decomposition reactor for a waste treating device by which a stuck material can be removed to prevent the heat transfer efficiency of the heat transfer surface from lowering and perform effective thermal decomposition, which stuck material having been stuck on the inner wall surface of a jacket and being about to be carbonized by the melting of synthetic resin or the like in waste generated in a thermal decomposition reaction process.

A thermal decomposition reactor 1 for a waste treating device has a heating pipe 4 for heating waste to thermally decompose it arranged in a horizontal rotary drum 2, and the horizontal rotary drum 2 is formed of a jacket 5 consisting of a double wall on the waste feeding side thereof. The jacket 5 and the heating pipe 4 are made to communicate with each other, and also a stuck material scraping member 6 is arranged adjacent to the inner wall of the jacket.