PURPOSE: To always convey a prescribed quantity, keep quality control time constant and prevent nonuniform drying, by detecting the increase or decrease in the conveyed quantity to move a discharge cylinder up or down.

CONSTITUTION: Grains in a drying column 1 falls into a discharge cylinder 2 while the grains are dried. The grains are then transferred in a conveying cylinder 3 by blades 17 attached to an endless chain conveyor 4. The quantity of the falling grains depends on the degree of the drying and the kind of the grains. When the transferred quantity of the grains in the conveying cylinder 3 exceeds a prescribed value, a detecting plate 19 hung from a rotary shaft 18 is thrusted by the grains so that the swing angle of the plate becomes larger than a prescribed value. At that time, a motor 11 which is controlled by a potentiometer M attached to an end of the rotary shaft 18 rotates forward to wind a rubber belt 6 upward with a roll 7 to elevate the discharge cylinder 2 toward the drying column 1. As a result, the quantity of the grains falling into the discharge cylinder 2 decreases. When the transferred quantity of the grains becomes smaller than the prescribed value, the motor 11 rotates in reverse to elongate the rubber belt 6 to move down the discharge cylinder 2. As a result, the quantity of the grains falling into the discharge cylinder increases.