PURPOSE: To enable good mirror-like finishing by making grinding process with use of magnetic fluid as grinding abrasive grains, in the grinding of nonmagnetic work of ceramics, glass and the like.

CONSTITUTION: At the starting up of a grinding machine 1, magnetic fluid 2 in an abrasive grain pot 3 is dripped onto a nonmagnetic work, and the work is ground. The exhaust fluid (mixture of the magnetic fluid 2 and ground powder of nonmagnetic work) as the result of the grinding work is sent to a separator 5, such as a centrifugal separator through an exhaust line 4, where large mesh ground powder 6 is separated from the mixture and taken away. On the other hand, residual mixture of fine ground powder adn the magnetic fluid is sent to a specific-gravity difference separator 8 through a line 7. A magnet 9 in the specific-gravity difference separator 8 applies magnetic force having a gradient to the magnetic fluid, thereby only the fine ground powder 10 is pushed upward due to increased apparant buoyancy the ground powder 10 and the magnetic fluid 11 are separated from each other, the ground powder 10 is expelled from the separator 8, and the magnetic fluid is recovered into the abrasive grain pot 3.