To prevent dust from being scattered by applying the constitution that each of a plurality of segment brushes is formed to have approximately triangular cross section, and an air flow passage formed between adjacent segment brushes is inclined for the radial direction of a brush holder.

When a cup type deburring brush rotates, the air flows into an air flow passage formed between adjacent segment brushes 7 having triangular cross section in the direction inclined for a brush radial direction. In other words, the air flows into the air flow passage between the adjacent segment brushes 7 in the slantwise direction from the periphery of the cup type deburring brush to the center thereof. As a result, dust is collected to the center of a brush holder on the air flow, and sequentially passes suction holes 12, gaps and through-holes 4 via brush holder fins, a suction device connected to the suction port of a dust suction casing, and the like. Thereafter, the dust is discharged outside via the suction port.