To provide a device capable of largely reducing spool fluctuation causing micro-vibration (background vibration) of a hydraulic actuator.

A micro-vibration reducing device consists of a hydraulic pump 21, a supply pressure (electric) feed back control means, a control servo valve 23, a hydraulic actuator, and a controller 26. The supply pressure (electric) feed back control means is arranged between the hydraulic pump 21 and the control servo valve 23. The pressure control controller 26 inputs the pressure value at the inlet of the control servo valve 23 as well as a pressure setting command value and outputs a control signal to an electromagnetic control valve 22. The electromagnetic control valve 22 regulates the pressure of the oil, which is sent from the hydraulic pump 21 to the control servo valve 23, based on the signal from the pressure control controller 26 and through PI operation. The control servo valve 23 controlled by the signal from the controller 32 takes in the pressure oil from the electromagnetic control valve 22 and discharges it toward the hydraulic actuator.