To prevent the deposition of waste caused by spout to the fourth opening, and the sticking of stems to a chaff sieve from the fourth opening, and to smoothen the flow of a selection air by keeping sufficient clearance between a return pan and the chaff sieve in a selection device having a gas cylinder fulcrum and the return pan arranged at the upper part of the chaff sieve.

The selection device 1 has a swinging selection body 25 having the chaff sieve 9 for sieving a material to be selected, threshed at a threshing chamber 2, and the return pan 10 covering the upper part of the chaff sieve 9. The upper part of the threshing chamber 2 is covered with a freely openable covering body 19, and the covering body 19 is constituted so as to be supported by a gas cylinder 21. The lower side fulcrum of the gas cylinder 21 is formed at the upper part of the chaff sieve 9. The return pan 10 is arranged so as to overlap with the gas cylinder 21 in the front and side views.