PURPOSE: To improve the dimensional accuracy of a material to be rolled without displacing a rolling roll in its axial direction by arranging two pairs of angular contact ball bearings in back-to-back duplex form respectively.

CONSTITUTION: When a thrust load is burdened in the arrow B direction, the positions of balls 54a are restrained by the high level face of the right side to sustain the thrust load. Further, on the contrary, the left side of a rolling raceway-groove of balls 54b is made to be high level in an outer ring 52b of angular contact ball bearing 42b, to sustain a thrust load of the arrow A direction by said left-side high-level face. Angular contact ball bearings 56a, 56b are also provided with the angluar contact constructions in the same direction as those of the bearings 42a 42b to sustain the thrust load to the direction B by the bearing 56a and the thrust load of the A direction by the bearing 56b.