PURPOSE: To execute the polishing of a granular body efficiently without increasing the rotation speed of a grinding head and elongating the processing time and to easily contact additional installation on the dust collection equipment provided already.

CONSTITUTION: A grinding head 8 in the longitudinal arrangement is provided on a grinding unit 2, the air flow system fluidizing a granular body with its floating is given on the circumference thereof, a dust transfer unit 4 having the air transfer mechanism of the dust separated from the graunlar body of after grinding is provided and the system feeding to a main dust collecter with the dust being recovered therein is given. The processing efficiency by the polishing utilizing the whole peripheral face of the grinding head 8 is improved and it can easily be installed in addition even to the dust collection equipment provided already.