To prevent the sorting trouble of an oscillating and sorting plate while contriving making operation easier.

A distribution boundary position of hulls/unpolished rice in sorted grains on an oscillating and sorting plate 15 is detected by a hulls-unpolished rice discriminating sensor 30 in hulling work, and the partition position of an unpolished rice partition plate 18 is detected by an unpolished rice partition plate transfer position detecting sensor. Next, by the detected hulls/unpolished rice boundary detection position, based on a prescribed calculation formula, the related partition position of the unpolished rice partition plate 18 is calculated and determined to transfer it. Next, whether partition position control of the unpolished rice partition plate 18 is automatic control operation or manual control operation is determined. When it is the automatic control operation, whether the manual control operation of the unpolished rice partition plate 18 is encountered two or more times within prescribed time in the same direction of the shake-upward side 15c or the shake-downward side 15d or not is determined. When the manual control operation is encountered two or more times, the automatic control operation of the unpolished rice partition plate 18 is stopped to switch the operation of the unpolished rice partition plate 18 to the manual control operation.