To improve workability by making the arrangement of hydraulic piping for feeding oil to an actuator, the same on the turning base side and the boom side, and mounting the piping in one lot on the turning base side.

The arrangement of hydraulic piping 38 formed of piping 38A of a boom actuator 19 and other piping 38B of an arm actuator 20 or the like is made the same on a turning base 3 side and the boom 14 side, and is put together in one place on the turning base 3 side mounted by a clamp 39. The clamp 39 has a clamping part 39A for the piping 38A on an upper stage, and a clamping part 39B for the other piping 38B on a lower stage. The clamping parts 39A, 39B are made common by a base plate 39C. The clamping parts 39A, 39B press the piping from the upper and lower sides, and the mating face is fastened by a bolt 39D. Piping connecting errors can thereby be reduced, and piping clamping work can be simplified.