PURPOSE: To secure an optimal flow rate by providing a blow priority valve to send a liquid preferentially to one operating tool of a single pump operating two operating tools and a switch valve to send the total volume of the pump between the priority valve and the pump.

CONSTITUTION: A single pump P having a capacity enough to operate the first and second operating tools 2 and 3 is provided, and a blow priority valve 23 to send liquid preferentially to one of the tools 2, a relief valve 21, and a switch valve 22 are provided for the discharge circuit 20 of the pump P. The switch valve 22 to send the total volume of the pump P to the tool 3 by switching by the pilot pressure of the other tool 3 is provided between the valve 23 and the pump P is provided. An optimal flow rate for both operating tools 2 and 3 can thus be secured by the single pump P, enhancing the efficiency of operations. Safe and easy operations can thus be performed.