PURPOSE: To enhance the workability at a slope by compensating the angle and the height of a bucket with values corresponding to a vehicle inclination angle in accordance with output signals from a bucket posture detecting means and a vehicle inclination angle detecting means.

CONSTITUTION: In the case of excavation at a slope having a down-grade, a controller 16 receives a vehicle inclination angle detected by an inclination sensor 15, and then carries out determination in accordance with this received signal, and a boom cylinder 8 is extended in the vicinity of the terminating point of one cycle of automatic excavation. Then, a boom 4 is rotated upward by a predetermined angle. Further, the position of a bucket base end pin P is shifted upward by a length H1, and the opening of a bucket 6 is set to be substantially horizontal. Further, in the case of excavation at a slop having an up-grade, a bucket cylinder 10 is extended similarly, and the rotation of the bucket 6 is adjusted so as to set the opening face thereof to be substantially horizontal. With this arrangement, it is possible to prevent insufficient lift-up of the bucket and dropping of a load.