PURPOSE: To exactly perform linear excavation of the ground by making the correction of the excavation gradient during excavating operation easier by providing a excavation gradient fine regulator in parallel with the excavation gradient setter of an input unit.

CONSTITUTION: On the basis of outputs from detectors 18, 20, and 21 to detect the inclined angle Ψ0 of vehicular body, inclined angle β of a boom 2, inclined angle α of an arm 3, and inclined angle γ of a bucket 4 and also of outputs of a boom operating lever 5, an arm operating lever 7, and a slope angle setter 9, the cutting blade of the bucket 4 is controlled along a linear locus by a control circuit. In such a control circuit, an excavating speed command pedal 13 and an excavating gradient correction lever 11 are provided to the input unit 100. An excavating speed command value Vt, a vehicular body inclined angle Ψ0, an excavation gradient set value , and an excavation gradient correction value are put in the bucket tip speed arithmetic unit 17 of the controller 200. Preset excavation gradient can thus be easily regulated during the excavating operation.