PURPOSE: To clean a heating surface, by a method wherein a cleaning liquid is sealed in a chamber to be cleaned, is heated and pressurized by a high-temperature heat-releasing medium contained in another chamber, and the former chamber is rapidly opened, thereby ejecting the liquid together with heat transfer hindering substances.

CONSTITUTION: A connector 41 is connected to a water-supplying pipe 44 and an oil-supplying pipe 45 through valves 42, 43, while a connector 51 is connected to an oil outlet port 3, and is connected to a water-discharging pipe 54 and an oil- discharging pipe 55 through valves 52, 53. A residual oil is drained through a drain valve, the valve 42 is opened, water is fed into a lubricating oil chamber 8 until it flows over through a relief valve of a pipe 9, and the valve 42 and the relief valve are closed. Heated steam is fed into a steam chamber 15 to heat and pressurize the cleaning liquid, until a pressure gage for a pipe 10 indicates an appropriate pressure. Then, the heated steam is stopped, and the valve 52 is rapidly opened, thereby ejecting the cleaning liquid together with the heat transfer hindering substaces. These operations are repeated several times, whereby the heating surface 6 can be cleaned in a short time.