To provide a threshing machine enabling smooth movement of a waste culm discharged from a threshing chamber along an inclined flow plate by coating at least the surface side of the flow plate constituting a fourth port with a water-repelling material having water-repellency and sliding property, thereby repelling water, preventing a surface deposition of straw dust and improving threshing efficiency.

A culm is clamped and transferred with a feed chain 3 into the threshing chamber 2 to perform threshing work, the threshed material is separated into grains and dusts by a shaking sorter 7 in a separation air channel, and threshed culm is discharged at an end of the threshing chamber 2 through a waste culm port 2c to the funnel-shaped fourth port 10 formed of flow plates 26, 29 and discharged from the machine. In the threshing machine 1 having the construction, at least the surface of the flow plate constituting the fourth port 10 is coated with the water-repelling material 33 having water repellency and sliding property.