To provide a controller of a multiplate clutch for improving a traveling feeling of a combined harvester and a thresher.

Side clutches 23L, 23R transmitting a linear driving force to right and left traveling devices in a manner to be freely turned on or off are provided in a linear driving force transmission system of a transmission 11. Multiplate clutches 36, 43L, 43R controlling a pressing force of a disc by hydraulic pressure are provided in a turning and driving force transmission system. Oil with a predetermined hydraulic pressure is supplied according to an operation position of a steering lever, and the turning and driving force is transmitted to the traveling device under a condition that the side clutch is turned off. A controller of an electromagnetic proportional valve supplying oil to the multiplate clutches 36, 43L, 43R is provided with an inclination control means controlling the electromagnetic proportional valve for gradually increasing the hydraulic pressure of the oil to the multiplate clutches when the steering lever is operated to a predetermined operating position, and for controlling the electromagnetic proportional valve to reach the hydraulic pressure set corresponding to the operation position of the steering lever after the predetermined time has elapsed.