To provide a back up roll device which is effective to reduce rotational torque.

In this back up roll device 11, roller bearings 14 for loading radial load and a ball bearing 15 for loading thrust load are interposed between a roll 13 and a shaft 12. One ball bearing 15 is arranged only on the side of one end in the axial direction. This ball bearing 15 can support thrust load in both directions of the axial direction and is fixed in both directions of the axial direction to the roll 13 and the shaft 12.