A hydraulic forceps system includes: robotic forceps including a gripper, a first piston coupled to the gripper, a first cylinder forming a first pressure chamber together with the first piston, the first pressure chamber being filled with a hydraulic fluid, a second piston, a second cylinder forming a second pressure chamber together with the second piston, the second pressure chamber being filled with the hydraulic fluid, a communication passage through which the first pressure chamber and the second pressure chamber communicate with each other, and a motor that drives the second piston via a linear motion mechanism； a control device that controls the motor based on a command position for the first piston； and a position sensor used for detecting a position of the second piston. The control device includes: an observer that derives an estimated position of the first piston based on the position of the second piston detected by using the position sensor； and a position controller that derives a target rotational speed of the motor based on a deviation between the estimated position of the first piston and the command position.
