A waste oil refining plant recycles waste oil, oil sludge and antifreeze solution supplied from various factories. By using the Okadora Vacuum Dryer, it is possible to dry under very high vacuum conditions and refine the wastes into heavy, medium and light oil respectively. It is impossible to achieve such high vacuum conditions with a traditional waste oil refining apparatus. The waste gas produced by this operation can be treated at Teinenpi Deodorant Furnace under high temperature and by oxidization can be rendered odorless and harmless and safely emitted into the atmosphere.