PURPOSE: To perform remote operation by small operation force regardless of the magnitude of a load and the distance-between a driving section and driven section.

CONSTITUTION: A driving section A is provided with a servo valve piston 1 in which a switch valve 4 which can be operated by an operation handle 17 is fittingly inserted and a servo piston 2 mechanically connected to the servo valve piston 1 through a piston 5, and a driven piston 8 is provided in the driven cylinder of a driven section B. The driving section A and driven section B are connected by connecting pipes 22 and 23, and on the other hand, the pressured oil of a pump unit E is supplied to the driven section B directly by directly manually operating the switch valve 4 by means of the operation handle 17 or by activating the servo piston 2 of the driving section A to make it possible to drive a large load by operating a lever 10 with small operation force.