PURPOSE: To provide an apparatus for converting waste plastics into oil and capable of heat-cracking waste plastics with small amount of fuel in high efficiency to obtain an oily substance having improved uniformity.

CONSTITUTION: A melting chamber 3 for melting waste plastics is formed in an end of a heating furnace 1 heated with a burner 2. The molten plastic material in the melting chamber 3 is supplied to a heating chamber 4 furnished with a stirring means 12 and formed in the middle of the heating furnace 1. The other end of the heating furnace 1 contains a heat-cracking chamber 5 to effect the heat-cracking of the molten plastic material supplied from the heating chamber 4 to generate a gasified product, which is reformed to an oily substance having desired composition in a reaction chamber 6 provided with a reaction catalyst layer. The melting chamber and the heating chamber are made to be closable and the supply of the molten plastic material is carried out taking advantage of the vapor pressures generated in these chambers. The releasing ports of safety valves 17 attached to both chambers are preferably connected to a condenser 19 connected to the outlet-side of the reaction chamber 6.