PURPOSE: To enhance the working efficiency by absorbing floating dust being generated when the dust on a floor is swept with a main brush by a blower to stick it on a filter, and flowing a part of air-stream to be discharged to the deepest section from box inlet.

CONSTITUTION: A dust box 3 keeping the dust of a main brush 2, blower 4 and filter 5 are provided, and a nozzle 10 is provided to the upper side of an inlet 3a of the box 3 in the direction of the deepest section 3b. A blower duct 11 is connected to an air-discharge port to get out into the air outside a car, a duct 11b is connected to an air inlet of the nozzle 10, and sealant 12 is stuck to prevent the leakage of air. A partition plate 13 is provided to the inside of the box 3, and an edge section of the deepest section 3b is separated from the internal wall surface of the box 3 to supply air from a dust collection room 3d to a filter room 3c. According to the constitution, the dust can be sent to the rear of the box to increase dust collecting capacity.