The utility model provides a grain discharging device of a combine harvester. According to the grain discharging device, the swing angle of a discharging trough can be changed easily without wasting time and labor. The discharging trough (50) is arranged at the upper end of an upward feeding conveyor (40) through a swing supporting shaft (62), wherein the upward feeding conveyor (40) conveys grains stored in a grain box (5) upwards, and the discharging trough (50) can swing freely. In addition, through the arrangement of a driving mechanism (D), the discharging height of the grains flow down under guidance of the discharging trough (50) can be adjusted freely, and the swing gesture, with the swing supporting shaft (62) as a center, of the discharging trough (50) is set through the driving mechanism (D).
