PURPOSE: To accurately control the locus of the claw edge of a bucket by controlling the attitude of the bucket in such a way as to make the direction of excavating resistance to be received by the bucket conincide with the movement direction of the claw edge.

CONSTITUTION: When only the operating lever of an arm is operated, signal is sent out from an operation detector 21 and stored as a target height h0 in a memory 22 and sent out. A boom cylinder 12 is controlled by a controller 24, the height (h) of the claw edge 3a of the bucket is kept constant, and the locus of the claw edge becomes horizontal. Excavation resistance F is obtained by a resistance arithmetic unit 27, the angle θ between the direction of the excavation resistance and the horizontal direction is obtained by an angle arithmetic unit 28, and the bucket cylinder 5 is controlled by the controller 29 so that the angle θ is zeroed. The direction of the resistance F is thus made to conincide with the movement direction of the claw edge 3a.