To carry out scavenging works on a passage, etc., narrower than the breadth of a rotary brush by installing the rotary brush in a rockable manner and fixing the rotary brush at a desired angle by a knock pin, etc.

A pair of left-right rotary brush support plates 4 are mounted downwards to the lower sections of both left-right side sections of a frame 1, and a pair of upper and lower brackets 5 are fixed horizontally on the insides of the support plates 4. U-shaped rotary-brush mounting members 7 are inserted among the brackets 5 in a side view, in which rotary brushes 6 are set up downwards in the fronts, and the front ends of connecting rods 8, in which base ends are connected to the members 7, are attached pivotally to the interior sections of the brackets 5 by pivotally support bolts 10. Consequently, the connecting rods 8, the members 7 and the rotary brushes 6 are brought to a rockable state to the left and the right while using the pivotally support bolts 10 as supporting points. When the rotary brushes 6 are moved to the inside, knock pins 11 are detached from through-holes 5a, the members 7, etc., are rotated to the inside while employing the pivotally support bolts 10 as the supporting points, the through-holes of the members 7 and through-holes 5b are communicated, and the knock pins 11 are inserted and fixed again.