PURPOSE: To absorb a reaction at time of reaping as well as to control any possible rocking motion in a machine body by installing a side transmission case in one side of an axle in a main wheel, and attaching a side wheel interlockably to a tip of this transmission case, in a one-wheel traveling power reaper.

CONSTITUTION: In this one-wheel traveling power reaper 1, power of an engine 11 is transmitted to a main wheel 14 via a chain in a travel transmission case 13 after being shifted by a transmission 12, whereby a machine body is traveled. Simultaneously power of the transmission 12 is transmitted to a cutting edge 17 via each of power primary and secondary transmission cases 15, 16, thus reaping takes place. In the above constitution, a side transmission vase 18 is installed in one side of the main wheel 14, while a side wheel 19 is attached to a tip of this case. With rotation of the main wheel 14, the side wheel 19 is rotated via a chain in this side transmission case 18 installed in this axle. With this constitution, any possible reaction at time of reaping is absorbed, thus rocking motion in the machine body is controlled.