PURPOSE: To improve segregation efficiency by bringing synthetic resin vesicant particles in contact with solid-suspending solution to allow the suspending solid adhere to surface of the synthetic resin vesicant particles so that clogging trouble of a filter and fall out of the filtering material can be eliminated.

CONSTITUTION: Segregating operation is carried out in such a manner and an order as to pass a solution through a line 3, a filtering material layer 1 and a draining line 6, and suspending solid in the solution us segregated and filtered at the filtering material layer 1. A vesicant particles-containing filtering material on which the suspending solid adhered is segregated from the filtering layer 1 to be filtered and then precipitates to the mid-section ot the bottom of a precipitaion tank 8. When volume of vesicant particles having been segregated and pricipitated exceeded the prescribed volume and therefore filtering capacity has been deteriorated, the lines 3 and 6 are closed for agitation of the tank with an agitating device 2 so that the solid-bearing vesicant particles are fluidized, cleaned and rejuvenated. By conducting these operations continuously, the solids having been turned into flock can be discharged through the line 5 at an appropriate time.