PURPOSE: To suck and recover almost all dust generated by cutting by installing a dust collecting brush in an end part of a cover body communicated with a sucking cylinder body.

CONSTITUTION: A peripheral necessary part of a rotary cutter 2b is covered with a cross-sectional almost U-shaped cover body 1a, and a dust collecting brush 3 installed on the cover body 1a contacts with a road surface R, and a partition is formed between the road surface R and the cover body 1a by the dust collecting brush 3. Thereby, suction force generated by actuation of a sucking device can sufficiently act on the road surface R. Thereby, dust S generated when the road surface R is cut by rotating the rotary cutter 2b is sucked in the cover body 1a by being guided by the dust collecting brush 3. Since the dust S sticks to the dust collecting brush 3 and blocks up a clearance between brush hairs of the dust collecting brush 3, an entrance of outside air into the cover body 1a at sucking time is reduced, so that the suction force is further strengthened.