In this combine, an oscillatory sorter 26 for gravity sorting and a winnower fan 29 for wind sorting are disposed as a grain sorting mechanism 10 below a threshing cylinder 9a of a threshing unit 9. The combine is provided with: a first countershaft 76 extending from one of the left and right sides of the threshing unit 9 to the other side; and a second countershaft 104 positioned in front of the first countershaft 76. An auxiliary air supply fan 170 is disposed below a threshing port 9a toward the front side of the threshing unit 9 and in front of the winnower fan 29. The auxiliary air supply fan 170 is configured to be driven by a winnower drive mechanism 186 for transmitting power from the second countershaft 104 to a winnower shaft 100 of the winnower fan 29.
