PURPOSE: To prevent cereal grains from being jammed in an equipment having a spiral grain lifter in an oblique cylinder, by providing an overflow return port, a husk return opening and a push-in opening sequentially upwards in the peripheral wall of the cylinder.

CONSTITUTION: When unhusked rice grains are supplied into a push-in hopper 29, the grains flow into a cylinder 17 through a push-in opening 30 and are then moved up by the rotation of a spiral conveyor 19 so that the grains go into a feed hopper 8. The rice grains are then husked between rubber rollers 2, 3 and flow into an air sorter 4. The air-sorted husks are discharged to the outside of a machine. Unripe rice grains are taken out by a secondary conveyor 6. Mixed rice grains are taken out by a primary conveyor 5 and supplied into a horizontal separation cylinder 10. When the feed hopper 8 is filled with the unhusked rice grains, the grains push up a lid 22 by the pressure of the grains and flow out into an overflow chamber 27 through an overflow hole 21 so that the grains are returned to the cylinder 17 through an overflow return port 28.