To lessen clogging and to enhance sieve efficiency by mounting a chute which divides the transverse direction of vibration sieves at the bottom end of the space delineated and formed by the inside surface of a casing and a weir plate, arranging the long sides of rectangular mesh openings in the flow direction of raw materials and providing the apparatus with a closed circuit for returning the plus sieve products to a swiveling type crusher.

The sieving nets of the vibration sieve 70 are so arranged that the rectangular sieve openings are formed on both upper and lower stages and the long sides thereof are along the raw material flow direction. A dispersion device 60 is an apparatus for evenly dispersing and supplying the crushed products in the transverse direction of the vibration sieve 70 at the time of supplying the crushed products of the vibration type crusher 40 to the vibration sieve 70 by a belt conveyor 50. This apparatus is disposed between the belt conveyor 50 and the vibration sieve 70 and the inside of the casing is equally divided by the perpendicular weir plate. As a result, the raw materials supplied at random to the inlet aperture of this dispersion device 60 are nearly equally distributed in the transverse direction of the vibration sieve 70. The plus sieve products of the lowermost sieving net are segmented to arbitrary ratios. One of the segmented products are transferred to a return line and the other to a product line.