PROBLEM TO BE SOLVED: To prevent that an object to be treated is discharged from the back of a machine body while not being applied with fall-down treatment at an oscillation sorting part even in a farm field which is adverse in a condition that the machine body is inclined in the fore-and-aft direction, and the discharged object to be treated causes a grain loss.SOLUTION: A combine comprises: a fin drive motor 46 (opening change means) which changes openings of fins of a chaff sieve an inclination sensor 45 (inclination angle detection means) which detects an inclination angle of a machine body in the fore-and-aft direction and a control part 40. When a first fin opening condition is established on the basis that the inclination sensor 45 detects that the machine body is in a droopy posture, the control part 40 controls the openings of the fins so as to be enlarged by the fin drive motor 46. The first fin opening condition is established by the fact that, for example, the inclination sensor 45 detects that the machine body is in the droopy posture, also detects that the machine body is in the droopy posture continuously for a prescribed time, and after that, detects that the machine body is returned to a horizontal posture.
