PROBLEM TO BE SOLVED: To provide arc melting equipment capable of thermally efficiently melting an iron source and controlling the supply of the iron source from a preheating chamber to a melting chamber, and to provide a method of operating a molten metal using the arc melting equipment.SOLUTION: The arc melting equipment 1 includes a melting chamber 2 for melting an iron source, a shaft type preheating chamber 4 disposed with directly coupled to the melting chamber 2, and an electrode 3, and the equipment 1 is characterized in that: a bottom face of the chamber 4 is formed to have, at least a part of the bottom face, an inclined bottom face 7a having an inclination downward to the melting chamber 2; a shaft frontage dimension H is set to the optimum value for controlling the supply of the iron source; a push-out device 6 for moving the iron source in the chamber 4 in the direction to the chamber 2 is disposed below the chamber 4, and when the push-out device 6 is driven, the iron source is supplied from the chamber 4 to the chamber 2, and when the drive the device 6 is stopped, the supply of the iron source from the chamber 4 to the chamber 2 is stopped. The optimum value of the shaft frontage dimension H is set so as to satisfy a relationship of A≤H≤4A with respect to the maximum length A of the iron source.