To effectively remove a large quantity of dust which is produced when grains which are moved in a circulatory state are rubbed with each other and straw dust mixed in the grains when the grains are harvested by sucking the dust by means of a suction dust ejector at the time of drying the grains by means of a grain dryer.

In a dust ejector, the starting end side of an upper conveyor 3 which is put on a grain dryer 1 is connected to the bottom section of a discharge pipe section 21 connected to the top of the grain elevating tower 20 of an elevating/lowering machine 2 through an opening 24. In the pipe section 21, a guide plate 9 which regulates the grains discharged from the buckets 23,... of a bucket conveyor 22 in the tower 20 and jumping in the section 21 so that the grains may drop toward a receiving port 32 opened on the top face side of the starting end section of the conveyor 3 is provided. A winnowing section (y) which sorts dust from the grains is formed between the back face side of the guide plate 9 and the machine wall 210 of the pipe section 21 above the receiving port 32 on the starting end side of the conveyor 3 opened in the pipe section 21 by connecting and communicating the suction port 40 of a suction dust ejector 4 with the part of the machine wall 210 facing the opening 24 of the pipe section 21 above the downward free end of the guide plate 9.