Abstract: At least one lance is substantially vertically arranged above a hot-metal runner of a blast furnace so that the lowermost end of the lance is spaced apart by a prescribed distance from the surface of molten pig iron flowing through the hot-metal runner. A granular chemical composition adjusting agent for adjusting the chemical composition of molten pig iron is blown, through the lance, into molten pig iron by means of a carrier gas to adjust the chemical composition of molten pig iron so as to satisfy the following two equations:0.5H.ltoreq.H.sub.p <H (1)H.sub.p =M.multidot.G.multidot.exp(-r)/(D+0.02H.sub.L).sup.2 (2)In equations (1) and (2):H: depth of molten pig iron in the hot-metal runner (mm),H.sub.p : penetration depth of the granular chemical composition adjusting agent into molten pig iron in the hot-metal runner (mm),M: flow rate of the granular chemical composition adjusting agent (kg/minute),G: flow rate of the carrier gas (Nm.sup.