The invention provides a threshing processing apparatus. A purification device for purifying exhaust gas is configured between a thresher device and a grain box, the rigidity of a clamping portion ata thresher device side is improved, and the grain box located at the storing position can be reliably clamped at the thresher device side. A recessed portion (30) for storing at least a part of the purification device (17, 18) is formed at an intermediate portion of the up-down direction of a left sidewall (7A) of the grain box (7), a clamping portion (51) with a clamping part (57) is arranged atthe position of the right side of an upper wall (4E) of the thresher device (4), the clamping portion (51) and a winnowing cylinder (20) are connected through a first connecting part (56) extending along a forward-backward direction, and the left sidewall (7A) of the grain box (7) is provided with a clamping joint part (63) in clamping joint with the clamping part (57).