PURPOSE: To stably reduce the segregation and the center porosity, in a continuous casting method for producing a steel slab for hot-rolling by dividing the cast slab in the width direction.

CONSTITUTION: Surface rolling reduction is repeatedly executed at 1-25 mm rolling reduction quantity per one time at the position of 85-99% solidified ratio during the continuous casting. The surface rolling reduction quantity at the position divided in the width direction is made to be larger than the surface rolling reduction quantity at the other position by ≥1mm. By this method, the deterioration of material characteristic and the lowering of the yield accompanied with the width division are not wholly developed and the stability of quality of the product and the remarkable improvement of the productivity in the continuous casting process can be achieved in the extremely economical condition.