PURPOSE: To remove the burr generated at a cross part uniformly and surely by adjusting the abrasive grain density corresponding to the variation in the flowing speeds of an abrasive grain in the external magnetic field.

CONSTITUTION: In the case of removing the burr caused at the cross part of 1st and 2nd holes 1, 3 by utilizing the abrasive grain flow, the deburring capacity unevenness caused on the flowing speed unevenness of a media 6 at the crossing part is eliminated by increasing the abrasive grain density by a magnetic 5 in reverse proportion to the reduction of the flowing speed. Consequently, the deburring caused on this cross part can be performed uniformly and surely.