PURPOSE: To facilitate the recycling of finely ground matter consisting of a surface film and a base material by peeling off the surface film and the base material to ground them into different shapes by feeding the rough ground matter of a car bamper into a grinder under pressure along with air to cut the same by a rotary blade before finely grinding the same by jet vortex streams of air chambers.

CONSTITUTION: When a car bamper is subjected to grinding treatment to be regenerated and reutilized, the rough ground matter of the car bamper and air are fed into the casing 1 of a grinder at first from the inlet part 2 thereof. At the same time, the rough ground matter and air are sprung up by a rotary plate 8 by rotating a rotary shaft 3 at a high speed to cut the rough ground matter by the rotary blade 4. Next, the ground matter is passed through the gap between the casing 1 and a grinding part 5 to be introduced into small vacant chambers 6. The ground matter is ground by the jet vortex streams formed in the vacant chambers 6. At this time, the surface film layer 51 bonded to the base material layer 53 of the car bamper by an adhesive layer 52 is peeled off from the base material layer 53. Continuously, the ground matter is gradually raised to be discharged from a discharge part 7.