PURPOSE: To maintain the prescribed sorting capacity by changing and controlling the number of revolutions of a sorting cylinder largely and small according to a moisture value of dried unhulled rice by a controlling means.

CONSTITUTION: A sieve sortor 22 is constituted so that the sized unhulled rice falling through the slit holes formed to a rotary interlocking sorting cylinder 24 is separated and sorted from a foreign matter which remains in the sorting cylinder 24 and is discharged from a terminal side. The number of revolutions of the sorting cylinder 24 is changed and controlled largely and small according to the moisture value of dried unhulled rice by a controlling means 37. In other words, when the moisture value of unhulled rice to be dried is large or an elapsed time for drying is made little, rotation of the sorting cylinder 24 is slowly set. Therefore the slow turning of the sorting cylinder to the rotary direction can be made little in the discharge side of unhulled rice. On the other hand, when the detected moisture value is lowered or the elapsed time for drying is made large and a state wherein drying of unhulled rice has been progressed is shown, rotation of the sorting cylinder is made speedy. Thereby the prescribed sorting capacity can be maintained.