To provide a second crop-returning structure for a threshing apparatus ensuring improving separation efficiency or separation accuracy at a separatory section.

This second crop-returning structure for the threshing apparatus comprises the separatory section 3 for subjecting a treated product after threshed to separatory treatment and a screw-conveying type second crop-returning mechanism 19 functioning to elevate and return a second crop after separated by the section 3 to the separation initial end side of the section 3. In this structure, a cylindrical wall 32 externally enclosing the returning screw 30 of the second crop-returning mechanism 19 is provided with a porous part 33 for promoting disaggregating grains contained in a second crop through sliding contact with the second crop elevated by the returning screw 30. The second crop-returning mechanism 19 is equipped with a sidewall 36 defining, in between it and the cylindrical wall 32, a returning path 35 through which grains leaked from the porous part 33 out of the cylindrical wall 32 are guided to a returning port 34 provided on the cylindrical wall 32 and returned into the cylindrical wall, and a wind-causing means 40 for causing conveying wind for discharging dust contained in the second crop via the respective holes 41 of the porous part 33 and a dust-discharging port 37 provided on the sidewall 36 out of the thresher.