A numerical model was developed for the simulation of solidification structure formation during the continuous casting process of an Fe–0.7mass%C alloy. In this model, the cellular automaton method was combined with heat transfer calculation during the continuous casting process. The effect of electromagnetic stirring (EMS) during the continuous casting process was introduced as an increase in thermal conductivity in liquid. Furthermore, the effect of fragmentation of dendrites due to fluid flow during EMS was taken into account in the model as an increase in the formation of crystals. Simulations of grain structure formation in continuously cast billets with and without EMS were carried out, and the degree of fragmentation was evaluated from a comparison between experimentally observed and simulated macrostructures of the billets.