A cluster type multistage rolling mill (100, 100A, 100B, 100C) comprising: a pair of work rolls rolling a metal strip; an intermediate roll group supporting the work rolls; a plurality of divided backing bearing assembled shafts (A, B, C, D, E, F, G, H, I, J, K, L, M, N) supporting the intermediate roll group, the plurality of divided backing bearing assembled shafts each including a divided backing bearing (5, 34), a shaft (6, 35), and a saddle (7, 36); a housing (8, 25, 26, 29, 30, 39, 40) supporting the saddles; a changing carriage disposed on a work side of the housing, the changing carriage having rails capable of being loaded with the divided backing bearing assembled shafts, the cluster type multistage rolling mill characterised in that it comprises: wheels arranged on at least a drive side of the divided backing bearing assembled shafts and adapted to roll on the rails of the changing carriage; wherein the wheels and the rails are configured such that, within the housing, the divided backing bearing assembled shafts each can be moved via the wheels on one of a housing bore upper surface constituting the housing, spray frame upper surfaces, and the rails of the changing carriage, and outside the housing, the divided backing bearing assembled shafts can be extracted from within the housing or inserted into the housing by being moved on the rails of the changing carriage via the wheels. a pair of work rolls rolling a metal strip; an intermediate roll group supporting the work rolls; a plurality of divided backing bearing assembled shafts (A, B, C, D, E, F, G, H, I, J, K, L, M, N) supporting the intermediate roll group, the plurality of divided backing bearing assembled shafts each including a divided backing bearing (5, 34), a shaft (6, 35), and a saddle (7, 36); a housing (8, 25, 26, 29, 30, 39, 40) supporting the saddles; a changing carriage disposed on a work side of the housing, the changing carriage having rails capable of being loaded with the divided backing bearing assembled shafts, the cluster type multistage rolling mill characterised in that it comprises: wheels arranged on at least a drive side of the divided backing bearing assembled shafts and adapted to roll on the rails of the changing carriage; wherein the wheels and the rails are configured such that, within the housing, the divided backing bearing assembled shafts each can be moved via the wheels on one of a housing bore upper surface constituting the housing, spray frame upper surfaces, and the rails of the changing carriage, and outside the housing, the divided backing bearing assembled shafts can be extracted from within the housing or inserted into the housing by being moved on the rails of the changing carriage via the wheels. wheels arranged on at least a drive side of the divided backing bearing assembled shafts and adapted to roll on the rails of the changing carriage; wherein the wheels and the rails are configured such that, within the housing, the divided backing bearing assembled shafts each can be moved via the wheels on one of a housing bore upper surface constituting the housing, spray frame upper surfaces, and the rails of the changing carriage, and outside the housing, the divided backing bearing assembled shafts can be extracted from within the housing or inserted into the housing by being moved on the rails of the changing carriage via the wheels.