To provide a clamp system for fixing a work which is constructed to increase the ratio of a work area on a base plate, by simplifying an architecture of an oil passage formed on the base plate while securing the guidability of a piston rod of a hydraulic cinder for a clamp device.

Hydraulic cramp devices 3, 4 are formed with cylinder bodies 30, 50 integrated on a base plate 2 in a front-to-back direction, output members 31, 51 which include piston rods 32, 52 extending from the cylinder bodies 30, 50 to a surface of the base plate 2, guide members 34, 54 which are releasably fixed on the surface of the base plate 2 and reciprocally movably guide the piston rods 32, 52, and rod side cylinder end walls 41, 61 of the cylinder bodies 30, 50 releasably fixed on the base plate 2. First oil passage 10, 11 are formed in a wall part of the base plate 2 for supplying hydraulic pressure from a hydraulic feed device 7 to the cylinder bodies 30, 50 of multiple cramp devices 3, 4.