(57) A method of reducing widths of hot slabs by pressing with a pair of anvils. Each the anvil is formed with an entrance inclined portion having an inclined angle more than 10° but l ess than 18 ° on an entrance side of the hot slabs relative to an advancing direction of the hot slabs and with a parallel portion continuous to the entrance inclined portion. The hot slab is continuously pressed by the anvils to reduce its width to a predetermined width. In a preferred embodiment, the anvil is further formed with an exit inclined portion continuous to the parallel portion on an exit side of the hot slabs. After the pressing has arrived at a location of the slab near to its trailing end, the slab is further advanced to preform the tailing end of the slab with the aid of the exit inclined portion. Thereafter, the slab is once retracted and the remaining portiton of the slab is pressed in the same manner as the initial pressing. Thus a tongue at the trailing end of the slab produced when simply pressing and a fishtail at the trailing end produced with the exit inclined portions are cancelled with each other, thereby obtaining sound slabs devoid of any defects such as tongues, fishtails and cracks.