To control the temperature of a steel sheet to a target temperature with a high degree of accuracy even when the size or the line speed of the steel sheet is changed.

In a regression model, when the size of a preceding material is different from the size of a succeeding material or the line speed of the succeeding material is changed from the line speed of the preceding material, the variation of the size and the line speed is used as an input variable and the temperature fluctuation of the succeeding material according to the change of the size and the line speed is used as an output variable. The control apparatus 100 calculates the temperature fluctuation of the succeeding material by utilizing the regression model, and controls at least one of the target temperatures of the preceding material and the fuel flow delivered to a heating apparatus of a direct-fired continuous heating furnace based on the calculated temperature fluctuation of the succeeding material. That is, the control apparatus 100 directly predicts the variation of sheet temperature by utilizing the regression model instead of predicting the sheet temperature at the exit side of the heating furnace.