To provide equipment which makes it possible to effect thermal decomposition efficiently and economically without causing coking and without requiring an unnecessarily large reaction volume for melting and thermally decomposing a thermoplastic resin such as a polyvinyl chloride to separate and remove chlorine contained in the resin as hydrogen chloride.

The equipment consists of a reactor body 1 provided with a thermoplastic resin supply port 2 on the upper side at one end and a product discharge port 3 on the lower side at the other end, a hollow screw shaft 4 which turns by a driving mechanism around a central axis and has a spiral screw guide 9 around the periphery, a heating medium introduction mechanism, such as a burner, disposed at one end of the screw shaft 4, and a heating medium discharge mechanism, such as an exhaust screen 16, provided at other end of the screw shaft 4.