PURPOSE: To easily obtain a perfectly washed and dried powdery granule, by performing washing, the separation of the powdery granule and a solvent and the drying of said powdery granule in one apparatus.

CONSTITUTION: Powdery granule is contacted with a solvent under stirring in washing tank 1 to transfer the org. pollutant contained therein into the solvent which is, in turn, passed through a tank 4 from a filter part 16 through a liquid extraction port 15 and piping 18 and supplied to a distillation apparatus 2 through piping 9. The solvent recovered by distillation is subsequently supplied to the washing tank 1 again from piping 12 through a tank 3. When the washing of the powdery granule is finished, all of the solvent is withdrawn from the liquid extraction port 15 and the residual solvent is evaporated by heating to be returned to the tank 3 from piping 22. In addition, the dried powdery granule is taken out from a take-out port 17. As the result, the perfectly washed and dried powdery granule can be easily obtained.