PURPOSE: To make small reduction ratio of a transmission to constitute a compact mission case by constituting the device so that an accelerator lever is returned on the low speed side accompanied with a backward operation of a shift lever.

CONSTITUTION: Engine E torque is transmitted to a transmission in a running mission case M through a belt transmitting device B to drive a wheel W, and from the running mission case M to a transmission in a rotary case RK through a chain transmitting device C to drive a rotary cultivator K. In this case, an accelerator lever 6 and a shift lever 1 are cooperated through a contacting cooperating mechanism A composed of a contacting pin 7 additionally provided on the shift lever 1, a restraining member 8 to restrain a shift shaft 4 of a cultivating rotary device K, and wire 9. When the shift lever 1 is operated to backward R, the contact pin 7 presses down the restraining member 8, and the accelerator lever 6 is operated to the low speed side.