[OBJECT] To provide a fractionating device capable of stably fractionating powders such as cement raw materials by a simple configuration.
[SOLUTION] A fractionating device 1 for fractionating some of a powder (cement raw material) R falling in a chute (main body) 2, wherein the fractionating device is equipped with a screw conveyor 5 which passes through the chute, a part of a casing 5a opening inside the chute, and receives part of the powder from an opening (inlet) 5b, and a collision separation member (collision separation rod) 4 which is provided above the screw conveyor in the chute and collides with an object when an object of a predetermined size or larger falls, and prevents the object from falling directly onto the screw conveyor. A rotation shaft 5d of the screw conveyor may be inclined from 5° to 20° with respect to the horizontal plane so that the end of the discharge port side of the screw conveyor is positioned above the other end and may be equipped with a guide member 3 that guides the powder falling in the chute in the direction of the opening of the screw conveyor.