An air cleaning system comprising an air cleaner provided on a vehicle and a device which can keep the air cleaner in operation while a vehicle is parked, whereby the quality of air inside a passenger compartment of the vehicle can be improved while the vehicle is parked. Consequently, the quality of the air can be improved in advance before an occupant enters the vehicle, and the quality of the air can further be improved without fully depending upon the function of a catalytic filter of the air cleaning system.