A hydraulic servo actuator adapted to control a driven member in accordance with an operation of a servo circuit through which servo oil flows comprises a main cylinder and an associated piston, associated piston being reciprocable within the cylinder and the main cylinder divided by the piston into a first chamber and a second chamber which are adapted to be in fluid communication with the servo oil, a damper means provided within the main piston for dampening reciprocating movement of the main piston. A hydraulic servo actuator also includes a throttle means for imparting a predetermined restriction to the servo oil that flows between the second chamber and the damper means along the predetermined passage formed within the cylinder.