Provided is an auxiliary burner for an electric furnace that has high iron scrap heating effect by appropriately and efficiently burning a solid fuel such as coal together with a gas fuel. An auxiliary burner for an electric furnace 100 has a structure in which a solid fuel injection tube 1, a gas fuel injection tube 2, and a combustion-supporting gas injection tube 3 are coaxially arranged in order from the center. The front end of the solid fuel injection tube 1 is located inside the gas fuel injection tube 2 to form, between the front end of the solid fuel injection tube 1 and the front end of the gas fuel injection tube 2, a first space 4 for solid fuel and gas fuel premixing surrounded by the front end portion of the gas fuel injection tube 2.