PURPOSE: To prevent the occurrence of burr produced on the four corners of inside face of rolling material, by tapering the upper and lower work roll so as both end parts to have larger diameter and also, taper angle of the lower work roll is made larger than that of the upper work roll, at the time of carrying out hot broadside rolling of thick steel plate.

CONSTITUTION: Both end parts of the upper and lower work roll 1, 2, are tapered so as to have larger diameter for outside at the time of carrying out broadside rolling of the thick steel plate 5 by hot rolling. The taper angle α of the upper work roll 1 is made 5W10° and the taper angle β of the lower work roll 2 is made 2W3° larger than that of α. The burr a of iside face of four corners of rolling material, is prevented by carrying out the broadside rolling by the upper and lower work rolls having the tapered part of the above mentioned different angle.