PURPOSE: To improve operating properties and safety by detecting reaping load in reaping operation by reaping edge device and carrying out lifting and lowering control to reaping machine body so as to maintain the reaping load to proper load.

CONSTITUTION: Reaping load in reaping operation by reaping edge device 1 is detected by torque sensor 22. A lifting and lowering cylinder 14 is controlled by a controller 33 so as to maintain the reaping load to proper load. As a result, reaping edge device 1 is subjected to lifting and lowering control to a reaping machine body. When reaped stems and calms or mud packs in the reaped edge device 1 and reaping load becomes large, the device is controlled so as to automatically raise to proper load position and when the reaping load becomes small, the device is subjected to lowering control to maintain proper load. As a result, operating properties and safety of the device can be improved.