PURPOSE: To prevent the elliptical movement of a cutter by fixing the both edges of a shaft body and a cylinder through annealing and reducing the inetermediate gap and forming a spiral groove for introducing pressurized oil into the gap and widening the outside diameter of the cylinder by a hydraulic pressure, in a slitter shaft.

CONSTITUTION: A spiral groove 5 is formed onto the outer periphery of a shaft body 4, and the hole 7 formed in the direction of the axis center at the center part of the shaft body 4 and the groove 5 are connected through a hole 6. A cylinder 8 is installed outside the shaft body 4 and fixed through annealing with the shaft body 4 between X and Y, and the difference between the outside diameter of the shaft body 4 and the inside diameter of the cylinder 8 is designed to 0.05W0.08mm, and a little gap is formed. An air vent hole 9 is formed at one edge of the cylinder 8, and a groove 10 is formed to communicate to the spiral groove 5 of the shaft body 4. When this shaft is used, the difference between the outside diameter of the cylinder 8 and the inside diameter of a cutter is designed to 0.03mm or so, and after the cutter is inserted into the shaft, the outside diameter of the cylinder 8 is widened by a hydraulic power, and then the inner surface of the cutter is brought into contact over the whole surface, and the elliptical movement of the cutter can be prevented.