Nondeoxidized molten steel is removed from a steel converter and poured into a ladle. Carbon electrodes are submerged in a slag layer on the molten steel and are separated by a predetermined distance from the molten steel. The electrodes are energized to generate arcs with the molten steel. Argon gas is blown into the molten steel through a lance submerged in the molten steel to stir the molten steel with the gas. The molten steel is arc-heated and at the same time stirred. Carbon in the molten steel reacts with residual unstable oxygen in the steel to deoxidize the molten steel. The molten steel is also decarburized, thereby preventing an increase in carbon content of the molten steel in the arc process.