PURPOSE: To automatically change rolls by traveling a pair of beams intersecting at right angles to the path line of a straightening machine along the path line and installing a vertically movable roll-clamping device to a trolley device traveling along the beam.

CONSTITUTION: The roll clamping device A is faced to a prescribed roll main shaft 2 of a roller straightening machine B and they are aligned. An air cylinder 19 for a shift and an air cylinder 17 for a hook are operated and arm pins 10 for the hook are engaged with the holes of a ring 6 at the point of a sleeve. The air cylinder 19 for the shift and the air cylinder 17 for the hook are operated in the opposite way to the preceding way, the straightening roll 1 and the sleeve 4 are pulled up integrally, slided and moved to a mandrel 3. The trolley device and the beam are traveled and moved to a spent roll storing base, the air cylinders 19, 17 are operated to push the rolls into the storing base. New straightening rolls 1 are taken by a similar operation into the mandrel 3, and carried as far as a prescribed roll main shaft 2 and assembled.