To prevent the unthreshed residue from remaining by releasing the nipping and conveying force of a conveyer to feed all of the rice plant stems into a threshing chamber in case when the reaped stems are short and have a possibility to remain unthreshed.

A reaped stems-nipping and conveying unit 5 is composed of a feed chain 3 along a threshing opening on one side of a threshing chamber and a nipping rail 4. In this case, a mechanism 15 for releasing the reaped stem nipping of the reaped stem-nipping and conveying unit 5 is made readily switchable between the nipping-released state and the actuating state, and the whole part of a nipping-released part of the nipping rail 4 is made movable away from the feed chain 3 in parallel.