To provide a control method of a refining furnace which avoids the bumping of steel bath.

In the control method of the refining furnace blowing at least O2 and coke toward the surface of the steel bath in the furnace body forming the steel bath composed of molten steel and slag by melting iron and steel, the temp. θm of the molten steel and carbon content Cm in the molten steel are calculated, and based on these molten steel temp. θm and carbon content Cm, a bumping iron oxide content F0 in the slag bumping the steel bath, is predicted. The slag is sampled from the steel bath and the actual measured iron oxide content F1 in the slag is obtd., and the coke blowing quantity and the molten steel temp. θm are adjusted so that the actual measured iron oxide content F1 becomes smaller than the bumping iron oxide content F0.