To provide a method for simply removing hydrogen chloride from a waste plastics contg. polyvinyl chloride with high percentage dehydrochlorination by mixing a waste plastics with a heating medium and directly heating and melting the mixture.

In a method for converting a waste plastics contg. polyvinyl chloride to an oil, in the step of melting and extruding a waste plastics by means of an extruder, the waste plastics is mixed with a high-boiling oil, and the mixture is melted and dehydrochlorinated by means of the extruder. The high-boiling oil may be a wax oil or the like and is pref. a fraction having a b.p. of 300°C or above. Specifically, e.g. the waste plastics and the wax are mixed with each other by means of an agitator in a charging hopper. The mixing ratio of the waste plastics to the wax is pref. 1:3 or more. The wax used is a solid or liq. wax produced in a system for conversion to an oil. The temp. of the wax fed into the hopper is pref. 150°C or below. However, it may be fed at 350°C if a suitable measure is taken to prevent ignition and cope with hydrogen chloride.