To prevent stopping of an engine by reducing a delivery flow rate of a variable pump when a rotating condition of the engine is a low level.

When an output value (a voltage value outputted in response to a turning angle of a throttle volume) of a throttle volume (a means to control a rotating condition of an engine) 104 is lower than a prescribed value, it is judged that a rotating condition of an engine 102 is a low level. A solenoid 120 is switched by the output value of this throttle volume 104, and delivery pressure P1 of a gear pump 122 is made to act on a shuttle valve 124, and this delivery pressure P1 is inputted to a variable pump 106 as negative control pressure. As a result, a delivery flow rate of the variable pump 106 is reduced only by the operation of this throttle volume 104.