To provide a method of manufacturing molten low carbon steel into a blank for sheet steel, with which the surface flaw and the nozzle clogging can stably be prevented by making deoxidation mainly using Ti so as not to produce alumina inclusion.

After decarburizing to ≤0.01% carbon content with a vacuum degassing treatment, the molten steel is adjusted to the components and also, the necessary total Ti adding quantity from the points of deoxidation and quality, is added in two or more divisions and thereafter, the molten steel further adding Mg, is cast. It is desirable to control the soluble oxygen content after adding Ti at the first time so as to become 10 to 100 ppm. Further, it is desirable to secure the time for floating up the inclusion for ≥30 sec till adding Ti at the next time after adding Ti at the first time.