Abstract: To preferably roll a hard material or an ultra thin material by more reliably supporting small diameter work rolls even under a transient condition such as when starting a rolling operation or when finishing a rolling operation, undriven both ends support rolls 9, 10, 11 and 12 are provided on outer sides of a width along which a maximum sheet width of strip passes on a barrel portion of the work roll 3, to be opposed to each other at an entry side and a delivery side of respective end portions to thereby press and support the work roll. Further, hydrostatic bearings 21 and 23 are installed at central portions of both side barrels of the work roll 3, and fluid such as oil is supplied from fluid pressure supply ports 25 and 26 to the bearing portions to thereby float up the work rolls 3 by forming gaps between the hydrostatic bearings 21 and 23 and the work roll 3 and support the work roll 3 in horizontal direction in noncontact.