A molten metal component estimation device comprising: an input device configured to receive: first measurement results regarding temperature and a component concentration of a molten metal before a blowing process starts or during the blowing process in a refining facility; and second measurement results regarding a flow rate and a component concentration of an exhaust gas discharged from the refining facility; a model database configured to store model expressions and parameters regarding a blowing process reaction in the refining facility; a material input-output calculation unit configured to estimate an amount of carbon and an amount of oxygen charged into the refining facility and an amount of carbon and an amount of oxygen discharged from the refining facility by performing an input-output balance calculation of carbon and oxygen based on the first measurement results, the second measurement results, the model expressions and the parameters; a physical reaction model calculation unit configured to estimate at least one of an amount of oxygen and an amount of carbon remaining in the refining facility by calculating at least one of an FeO amount in a slag and a decarburization amount in the molten metal based on the first measurement results, the model expressions and the parameters; and a correction calculation unit configured to: calculate a parameter for correcting a measurement value of the flow rate of the exhaust gas, a parameter for correcting a measurement value of the component concentration of the exhaust gas, a parameter for correcting a calculation value of the FeO concentration in the slag and a parameter representing the amount of carbon in the molten metal as first, second, third and fourth correction parameters respectively, from the second measurement results received by the input device and using the estimation results of the material input-output calculation unit and the physical reaction model calculation unit; and estimate the component concentrations in the molten metal and the slag, using the calculated first, second, third and fourth correction parameters. an input device configured to receive: first measurement results regarding temperature and a component concentration of a molten metal before a blowing process starts or during the blowing process in a refining facility; and second measurement results regarding a flow rate and a component concentration of an exhaust gas discharged from the refining facility; first measurement results regarding temperature and a component concentration of a molten metal before a blowing process starts or during the blowing process in a refining facility; and second measurement results regarding a flow rate and a component concentration of an exhaust gas discharged from the refining facility; a model database configured to store model expressions and parameters regarding a blowing process reaction in the refining facility; a material input-output calculation unit configured to estimate an amount of carbon and an amount of oxygen charged into the refining facility and an amount of carbon and an amount of oxygen discharged from the refining facility by performing an input-output balance calculation of carbon and oxygen based on the first measurement results, the second measurement results, the model expressions and the parameters; a physical reaction model calculation unit configured to estimate at least one of an amount of oxygen and an amount of carbon remaining in the refining facility by calculating at least one of an FeO amount in a slag and a decarburization amount in the molten metal based on the first measurement results, the model expressions and the parameters; and a correction calculation unit configured to: calculate a parameter for correcting a measurement value of the flow rate of the exhaust gas, a parameter for correcting a measurement value of the component concentration of the exhaust gas, a parameter for correcting a calculation value of the FeO concentration in the slag and a parameter representing the amount of carbon in the molten metal as first, second, third and fourth correction parameters respectively, from the second measurement results received by the input device and using the estimation results of the material input-output calculation unit and the physical reaction model calculation unit; and estimate the component concentrations in the molten metal and the slag, using the calculated first, second, third and fourth correction parameters. calculate a parameter for correcting a measurement value of the flow rate of the exhaust gas, a parameter for correcting a measurement value of the component concentration of the exhaust gas, a parameter for correcting a calculation value of the FeO concentration in the slag and a parameter representing the amount of carbon in the molten metal as first, second, third and fourth correction parameters respectively, from the second measurement results received by the input device and using the estimation results of the material input-output calculation unit and the physical reaction model calculation unit; and estimate the component concentrations in the molten metal and the slag, using the calculated first, second, third and fourth correction parameters.