PURPOSE: A rotor with projections of which the front edges are inclined, a nozzle for separating fibers and another nozzle for removing fibers are fitted to specific positions respectively to produce fully opened and small bulk-density fiber aggregations from lumps of fibers with high cohesion such as asbestos.

CONSTITUTION: A rotor 4 with projections 3 provided with the front edge 5 inclined so that the front edge goes more forward in the rotation direction of the rotor 2 than the ground edge is fitted in the front of the conveyor 1 for supplying fiber lumps to ensure the take-up of fibers from fiber lumps 14. A nozzle 6 for separating fiber jetting the air in the direction reverse to the rotation of the rotor is fitted to open fibers thoroughly. An additional nozzle 7 for removing fiber also is fitted more forward in the rotation direction of the rotor 4 than the top end of the nozzle 6 to blow off fibers 13 sticking to the projections and pile up them on the conveyor 12.