PURPOSE: To smoothen the slewing speed of an oil-pressure shovel as well as enable it to be controlled during the acceleration period by using a system in which the set pressure of variable relief valve is controlled while controlling a control valve for slewing by controlling the secondary pressure of a remote control valve by operating a lever.

CONSTITUTION: In an oil-pressure circuit for an oil-pressure shovel, a slewing preference type flow control valve 30 with a pressure compensator, having a preferential circuit 32 and a bleed-off circuit 33 on its outlet, is connected to an oil-pressure pump P2. Also, a control valve 22 for slewing is connected to the preferential circuit 32 on the downstream side of the flow control valve 30 , and also an arm control valve 24 and a boom convergent valve 25 are connected in parallel to the bleed-off circuit 33. In the flow control valve 30, the pilot oil- pressure circuit 45 of a lever-operable remote control valve 40 is provided with a relief valve 37 for setting pressures and a variable reducing valve 46 is provided between the remote control valve and the variable relief valve 37.