PURPOSE: To efficiently and stably perform a reaping work by preferentially subjecting a vehicle to a longitudinally horizontal control when a grain straw sensor does not detect grain straws or until the vehicle travels for a constant distance after the detection of the grain straws and preferentially subjecting the vehicle to a laterally horizontal control under conditions except the cases.

CONSTITUTION: When a vehicle travels from a butt to a non-reaping row and is largely tilted in the longitudinal direction, the vehicle is corrected to a horizontal state due to the longitudinally horizontal control preferentially set with a controller 21 wherein a pitching cylinder 17 is elongated or shortened by the action of pitching valve 18 caused by the front-lower or rear-lower solenoid 26, 27 on the basis of the detection of a longitudinal tilt sensor 33 and the control is performed based on the detected value of a longitudinal stroke sensor 36 and a longitudinal tilt standard value set in the controller 21. The vehicle reaps a non-reaped row and travels under the longitudinal horizontal control and after a grain straw sensor 31 detects the grain straws, the travel distance is counted with a vehicle speed sensor 30 to reap the grain straws for a constant set distance under the control. After the grain straws are reaped for the constant distance under the control, the control is switched with a laterally horizontal control and the reaping work is continued.