PURPOSE: To improve the rolling ratio when a charging pitch and rolling pitch fluctuate by varying the ejection ratios of the slabs from the 1st heating furnace and 2nd heating furnace.

CONSTITUTION: The slabs are alternately ejected from the 1st heating furnace (1) for heating the hot slabs supplied from a continuous casting device and the 2nd heating furnace (2) for heating the warm or cold slabs supplied from a slab yard and are rolled. The times when the slabs can be ejected from the furnaces 1, 2 are compared in the above-mentioned system, and a) the slabs are ejected from the furnace 1 when the former is earlier. The ejection time of the succeeding slabs to be ejected from the furnace 1 is set at the intended ejection time when the intended ejection time is later than the ejectable time and conversely said time is set at the ejectable time when the intended ejection time is earlier. b) The slabs are ejected from the furnace 2 when the former is later. The ejection of the succeeding slabs to be ejected from the furnace 2 is set similarly as with the furnace 1.