PURPOSE: To make the most of engine output constantly, by introducing pilot pressure to a tilting angle controller through fine control of a working machinery on one side of variable pump and making the excess flow of the pump absorbed by the other side of variable pump.

CONSTITUTION: A lever 11a is shifted halfway for fine control of working machinery on the side of a variable pump 2, then the pilot pressure of a pilot valve 11 is introduced into a pressure chamber 25 of a tilting angle controller 4 through a conduit 30 and a position F of a reversing valve 6. Since this pressure is lower than the original pressure of the pilot valve, a spool 18 is balanced in a position where the tilting angle of the variable pump 1 is large, if the discharge pressure of the pump 1 applied on a poiston 22 is kept unchanged. In other words, the excess flow of the variable pump 2 is absorbed by the other variable pump 1, which allows driving of the pumps with the maximum engine output for making the most of the engine output.