PURPOSE: To make safe and efficient roll change operation without requiring skill by combining the 1st and 2nd carriage and providing a roll supporting device and draw bar to the roll carriage and a roll stand and position detection and control device to the 1st carriage.

CONSTITUTION: The 1st traveling carriage 10 having the roll stand 14 carrying fresh rolls 12 is advanced in the direction perpendicular to the roll shaft in a housing 6 of a rolling mill and is stopped in the change operation position. Driving devices 20, 29 are commanded by the program of the control device 17 on the carriage 10 to run the 2nd traveling carriage 16 traveling the same direction as the traveling direction of the carriage 10 on said carriage and to lift the roll supporting device 26. The movement positions thereof are detected by detectors 21, 30 are detection heads 22, 31 and are inputted to the device 17, by which the positions are corrected to exactly determine the positions then to stop the carriage 16 and the device 26. The roll carriage 24 on the carriage 16 is manually advanced perpendicularly to the traveling direction of the carriage 16 to engage the top end of the draw bar 32 on the carriage 24 with the shaft end of the old rolls and the carriage 24 is retreated to draw out the hold rolls. The old rolls 13 thereafter imposed on the stand 14 by automatic and manual operations.