PURPOSE: To eliminate a need for resetting operation of an excavation surface being a target even when a working device body is moved and its posture is changed and to perform an automatic excavation work along a preset excavation surface.

CONSTITUTION: When, after by operating operation levers 32 and 33 installed in a driver's seat 30 by an operator, the back of a bucket 7 is brought into contact with a coarsely excavated slope to set an excavation surface Sd being a target and a linear excavation mode is selected and the operation lever 32 is operated, the bucket 7 is moved along the excavation surface Sd being a target based on information on the excavation surface computed by a microcomputer incorporated in a working device body to perform automatic excavation. When a hydraulic shovel is moved, data of the excavation surface Sd being a target is corrected according to a moving amount and a tilt change amount of the hydraulic shovel measured by an acceleration meter and a gyroscope, incorporated in the working device body. Based on the corrected data of the excavation surface Sd, the bucket 7 is moved to perform automatic excavation.