An apparatus for producing oil with waste synthetic resin according to the present invention comprises: a melting furnace for melting solid waste synthetic resin by impregnating same in a high-temperature oil; and a foreign substance removal facility for removing foreign substances such as metals from the waste synthetic resin melt supplied from the melting furnace. A main body constituting the foreign substance removal facility is provided with three stages of sedimentation plates, and foreign substances are removed from the waste synthetic resin melt by disposing the three stages of sedimentation plates in such a manner that the waste synthetic resin melt flows while overflowing and colliding between the three stages of sedimentation plates. The waste synthetic resin melt from which foreign substances are removed passes through a water pipe type heat exchanger constituting a heater for heat exchange. The heat required for heat exchange is supplied from a hot stove. The waste synthetic resin melt is heated up to a temperature suitable for thermal decomposition while passing through the water pipe type heat exchanger, and is then put into a pyrolysis furnace to be subjected to pyrolytic decomposition. Combustible gas components and oil vapor containing oil components are obtained by conducting the pyrolytic decomposition of the waste synthetic resin melt, and are sent to a cooler and cooled to obtain a desired oil.