To reduce working load when performing the maintenance and the replacement of a rolling roll by making easy the position restraint in the axial direction of the rolling roll.

The clamping device 10 for rolling mills includes a pair of clamping tools 23 for restraining the position in the axial direction of a roll chock 16 by pressing both sides in the radical direction of the roll chock 16 and a fastening device 24 which is installed between the pair of the clamping tools 23 and with which the position restraint and the release of the restraint of the roll chock 16 are executed by the pair of the clamping tools 23 by expanding and contracting in the longitudinal direction. The fastening device 24 has an actuator 32 which is provided with a cylindrical cylinder 35 connected to the side of one clamping tool 23 and a piston 36 connected to the side of the other clamping tool 23 and slid in the axial direction of the cylinder in the inside of the cylinder 35 by the pressure of fluid fed into the cylinder 35.