PURPOSE: To provide the title unit so designed that a specific constitution is used in the structure of a spiral elevation cylinder as the second unit, thereby enabling a threshing chamber to be easily slided even in using said elevation cylinder.

CONSTITUTION: A threshing chamber 9 with a threshing cylinder 11 and a wind- screening chamber 10 with a wind-screening unit are mutually dividedly formed and the threshing chamber is made detachable, and a secondary product produced by screening in the chamber 10 is returned to the threshing chamber 9 through a spiral elevation cylinder 17 to be put to recycling treatment again. In the title threshing unit constituted as the above, the following constitution is added: the spiral shaft 26 of said cylinder 17 is so designed as to be pullable upward, said cylinder 17 is divided into the upper and lower subcylinders 24 and 25, and the upper subcylinder 24 is made detachable along with the threshing chamber 9.