PURPOSE: To drive a plurality of actuators synchronously with high reliability by arranging a plurality of pistons in a plurality of cylinders and coupling respective pistons through a coupling shaft coupled with a driving means.

CONSTITUTION: A plurality of cylinder chambers 2 are formed in series in a casing 1 and pistons 3 are mounted slidably in respective cylinder chambers 2. The pistons 3 are coupled integrally through a coupling shaft 4 to be driven through a driving means 5 so as to couple pressurizing chambers 6 in respective cylinder chambers 2 with respective actuators 23. Since pressure oil is fed from the pressurizing chamber 6 to a pressure receiving chamber 23a of the cylinder 23 with constant pressure and constant flow, respective actuators 23 can be driven synchronously with high accuracy.