PURPOSE: To improve grain-removing effect, by placing plural spiral threshing drums in parallel in such a manner as to integrate the spiral part of the drum with the gap between the pitches and threshing the crops while transferring the whole crops to be threshed.

CONSTITUTION: Crops introduced into a threshing chamber 1 is transferred in axial direction with a pair of spiral threshing drums 4, 4' and subjected to the grain-removing action by the friction with receiving nets 2, 2'. Furthermore, the crops are pressed against the surface of the spiral circumference by the mutually integrated spiral members 3, 3'. The grain-removing action is generated by the kneading motion of the spirals with each other to improve the grain-removing effect.