PURPOSE: To efficiently strip off and remove a large quantity of dust, etc., deposited in an air cleaner by sending compressed air and pressurized water into the air cleaner airtightly held between a holder and a lid to remove the dust deposited on the filter surface from the inside.

CONSTITUTION: A large amt. of air from an air duct 10 and pressurized water from a water supply pipe 15 are introduced into the air cleaner W airtightly held by the air cleaner holder 7 and lid 25 to increase the pressure in the filter, and the wrinkle of the filter is smoothed. The pressurized water is uniformly sprayed over the whole surface of the filter at the same time and leaked to the outside along with the air, and the dust deposited on the inner and outer surfaces of the filter in layers is stripped off in the form of a scale and removed.