PURPOSE: To eliminate the need for installation of guides among rolling mills and to reduce the labor for maintenance and inspection by incorporating plural sets of rolling mills in single frame constitution secured on a foundation in such a way that the rolls of the mills are on one line thereby placing the stands of the adjacent rolling mills closely.

CONSTITUTION: Plural sets of horizontal rolling mills H1 and vertical rolling mills V1, V2 are assembled in single frame 1 closely together with housings 8, 8', 7 thereof. Therefore, the spaces between the rolls 6, 6' of the adjacent rolling mills H1, V1, V2 are reduced and the large compressive or tensile forces exerted upon the individual housings 8, 8', 7 by a material to be rolled are absorbed by the internal force in the respective stands or the stresses of the frame 1. As a result, there is no need for setting the strength of the housings 8, 8', 7 of the individual mills H1, V1, V2 and the rigidity around the leg parts and the need for installation of guides is eliminated.