To improve the control precision of a brown rice partitioning plate of an oscillating classifier.

The selection condition on the discharge side of an oscillating selection plate 15 is detected by an unhulled-brown rice discrimination sensor 30 to control the partition position of a brown rice partitioning plate. Every time when the sensor 30 detects the boundary of a prescribed distance and moves, the abnormality of the sensor 30 is judged by checking whether the boundary detection position of detection data is shifted to the proper value side or not, and when the sensor 30 is judged abnormal, the threshold value of unhulled-brown rice judgment of the sensor 30 is corrected. In this way, even when the variety is changed during work, the detection of the boundary position between unhulled rice and brown rice is correct, improving the control precision of the brown rice partitioning plate 18.