PURPOSE: To improve the accuracy of rolling without clattering in the supporting parts of roll shafts to be fitted with conical rolls by modifying the supporting mechanisms for gear shafts to be disposed with said roll shafts and bevel gears.

CONSTITUTION: A bevel gear 4 which is intermeshed with a bevel gear 28 of a planetary shaft 27 is supported freely turnably by means of a radial bearing 5 to a roll head 1, and a gear shaft 3 is supported freely turnably by means of a radial bearing 6 to a jacket 2. A thrust bearing 7 is interposed between the flange part at the forward end of the shaft 3, and the inner projecting part of the jacket 2, and the shaft 3 and the gear 4 are fixed in the thrust direction. A main radial bearing 11 is disposed in the forward end part of a roll shaft 8 coupled to a conical roll 9, and a main thrust bearing 12 and an auxiliary radial bearing 13 are disposed in the root end part thereof to support the roll shaft freely turnably with respect to the roll head 1 and freely movably in the thrust direction.