Abstract: A combine including: a grain tank that stores grains sorted by a sort unit that swings to sort grains fallen from a threshing cylinder unit; a yield measuring device that measures the amount of grain put in the grain tank; a unit yield calculation unit that calculates a unit yield per unit plot in a cultivated field; an opening degree adjustment unit that adjusts the opening degree of a chaff sheave of the sort unit in accordance with a threshing state of the threshing apparatus; a mode setting unit that sets a yield accuracy priority mode in which priority is given to accuracy of the unit yield calculation performed by the unit yield calculation unit; and a yield accuracy maintenance unit that in response to the mode setting unit setting the yield accuracy priority mode, forcibly fixes the opening degree of the chaff sheave at a specific opening degree.