To provide a device and a method for advantageously solving a problem that in the conventional case of changing the guide of the rolling mill, there is a risk from the viewpoint of safety due to the entrance of workers in the inside of the rolling line, and to provide a method by which the guide changing accompanying roll changing can be performed in parallel to the roll changing by using the provided device.

A guide changing device is composed of a master beam 24 which is made turnable while hanging the guide 3 of the rolling mill and a slave beam 21 which is made turnable in synchronism with the master beam while supporting a utility conduit 29 for supplying utility from the outside to the guide, and the guide changing is performed by using the same. In the case of the guide changing accompanying the roll changing, the measurement of the amount of the roll thrust is performed automatically (unmannedly).