PURPOSE: To regenerate a filter without damaging the same by spraying high pressure steam of definite temp. or higher or alkali degreasing solution- containing high pressure air of definite temp. or higher to the filter for compressed air clogged with oils and fats.

CONSTITUTION: A ceramic filter 3 used in an oil recovery device 3 to generate clogging by oils and fats is connected to a steam pipe 5 to allow steam 6 to flow to the filter 3 under high pressure. At this time, as this steam, high pressure air of 90°C or high or high pressure air of 90°C or higher containing an alkali degreasing solution is used. Whereupon, an oil component 7 is melted from the surface of the filter 3 to be flown. By this method, a heat shock is relaxed and the filter can be regenerated without being damaged or deformed.