a pyrolysis operation introducing waste plastics into a pyrolysis reactor and pyrolyzing the waste plastics to produce pyrolysis gas;

an oil production operation producing waste plastic pyrolysis oil by introducing the pyrolysis gas into a hot filter filled with a neutralizing agent;

a dehydration operation applying a voltage to a first mixed solution obtained by mixing the waste plastic pyrolysis oil, washing water, and a demulsifier to dehydrate the first mixed solution;

a hydrotreating operation hydrotreating a second mixed solution obtained by mixing the first mixed solution dehydrated in the dehydration operation and a sulfur source to produce refined oil from which impurities are removed; and

a distillation operation distilling the refined oil from which impurities are removed in the hydrotreating operation.