To eliminate heat energy loss due to partial release to a tank by regenerating the entire amount of return oil in a regenerative circuit of a hydraulic cylinder, and to prevent operation defects due to hunting of regeneration means.

In the hydraulic circuit of the hydraulic shovel, a regeneration valve 37 does not apply a system of partially releasing the return oil to the tank while drawing it on the way, but a system for switching between full-open and shutdown, whose control is performed on the basis of a bottom chamber side pressure Pc of a cylinder. Also, a first predetermined value for canceling regeneration during regeneration and a second predetermined value for starting the regeneration when the regeneration is canceled are provided to prevent the hunting, where the second predetermined value is the value substantially different from the first predetermined value.