To feed the flow rate of a pressure oil to an actuator according to the operation amount of an operation lever, and to increase the stability of the control, in the flow rate control device for the hydraulic pump of a hydraulic driving device having a center bypass type direction changeover valve.

A pressure produced by an operation lever device 6 is made into a positive flow rate instruction signal pressure signal Pc by detecting by a shuttle valve 13 and a signal line 14, the discharge flow rate of a hydraulic pump 1 is made into a pump flow rate signal pressure Pp by detecting by a pump flow rate detecting circuit 36 and a signal line 18, and the pressure generated by a throttle 37 is made into a center bypass passing flow rate signal pressure Po by detecting by a signal line 38. And a capacity control actuator 11 is controlled to make Pc=Pp-Po, by leading the signal pressure Pc and Po to the side to increase the capacity of the hydraulic pump 1 of a pump control valve 12, while by leading the signal pressure Pp to the side to reduce the capacity.