PURPOSE: To improve the efficiency of recovering ground powder by connecting a recovering pipe having an end opened to a space including a contact point of a grinding wheel or dresser and an object to be ground to a ground powder recovering part and providing an ejector in the connecting point of a pipe branched from a supply pipe and the recovering pipe.

CONSTITUTION: A chip dresser 1 rotates cutting edges 5 through a bevel gear 4 by the rotation of an air motor 3 driven by compressed air supplied from a supply pipe 2. A chip 12 of spot welding then is inserted into a dresser hole 13 until it abuts against the cutting edge 5 to carry out the dressing with the rotation of the cutting edge 5. The above of the cutting edge 5 is closed with space forming cover 14 to collect the ground powder spattered in the dressing, while a space in the cover 14 is adapted to communicate to a negative pressure part of an ejector 19 provided in a connecting point of a branch pipe 18 branched from an air motor 3 and the space through a recovering pipe 16 so that the ground power is attracted by the negative pressure to be recovered to a recovering part 17.