PURPOSE: To enhance the working performance of a construction machine having an upper slewing body, and improve workability at a restricted place.

CONSTITUTION: Blades 10 and 20 available as outriggers are fitted to the front and rear sides of the lower travel body 4 of a hydraulic power shovel equipped with an upper slewing body 1 having an operator's cabin 2 and a work machine 3. When a work is carried out using the machine 3, the front and rear blades 10 and 20 are kept in contact with the ground for use as outriggers. As a result, a balance load between a push-down force and a lifting force can be increased at the time of carrying out an excavation work with the machine 3, thereby improving a working performance. Also, when a working direction is changed for discharging the excavated earth, steering operation equal to or above 90 degrees is not required, as the blades 10 and 20 are provided at the front and rear sides. Thus, workability is improved particularly at a restricted place.