PURPOSE: To replace a roll easily and quickly by a comparatively simple structure, by providing inside an outside rails of a rolling machine, connected by a moving rail which can be displaced freely in a shunting position, and an off- line rail which can be displaced freely between a working position and a storing position.

CONSTITUTION: In case of a roll replacing operation, by a cylinder 13, moving rails 12, 12 are advanced from a position which is not obstructure to the up- and-down movement of a roll chock 20 in the course of operation of a rolling machine, and become on the same surface with end edges of fixed rails 10, 10. Subsequently, a wheel 21 of the chock 20 holding the roll is lowered on the rail 12 by a lifting device. At the same time, an off-line rail device 14 is operated, a frame 15 is raised perpendicularly by a cylinder 16, and upper and lower side rails 17, 18 are set to a position which is on the same surface with the inside and outside rails 10, 11 of the rolling machine, from a position which is equal to or lower than the floor surface. Subsequenly, work rolls 3, 4 are drawn out in a state that they have been connected in one body. When replacing a new roll, it can be performed by reversing the preceding steps.