To provide an operating method which can reduce an amount of power consumption and can easily adjust the carbon concentration in molten steel at the time of using carbon rich cold iron source such as direct reduction iron and cold pig iron along with iron scrap and melting them.

In a method for operating an arc furnace 1 including a melting chamber 2, a shaft-type preheating chamber 3 into which an exhaust gas generated in the melting chamber is introduced, and a cold iron source supply device 10 for the melting chamber, carbon rich cold iron source 21 is directly charged into the melting chamber by means of the cold iron source supply device and simultaneously iron scrap is charged into the preheating chamber such that the condition that iron scrap 20 is continuously present in the preheating chamber and the melting chamber is maintained, and the iron scrap and the carbon rich cold iron source in the melting chamber are melted by an arc 24, and at a point of time that at least molten steel 22 of one heat is stocked in the melting chamber, the molten steel is tapped under the condition that the iron scrap is continuously present in the preheating chamber and the melting chamber.