To efficiently refine copper having a high purity by adding concrete waste material as flux into molten copper and as necessity requires, the other component to form FeO-CaO-SiO2 three-component system slag.

At the time of melting and refining a high quality copper scrap, a concrete waste material crushed into the suitable size as flux and as necessity requires, SiO2 component and FeO component, are added. By this method, on the surface of molten copper, the FeO-CaO-SiO2 three-component system slag, desirably the slag having the composition of 31-60wt.% FeO, 28-35% CaO and 31-40% SiO2 is formed. In the case of using the slag having such a composition, the slag having comparatively low m.p. about 1100-1200°C, and excellent in impurity removal performance, is obtd. and the refining can efficiently be executed under good treatment. It is desirable that the flux quantity if added so as to form the slag quantity having about 20-30wt.% to the molten copper.