A method of refining metal to be processed to a high degree of purity by heat-melting the metal in a melting furnace in the form of a metal crucible placed in a vacuum vessel. The method includes evacuating prior to melting, preheating the inside of the entire vacuum atmosphere including the inner wall surface of the vacuum vessel, component parts inside the vessel and the like in order to keep the total pressure within the vessel at 1.times.10.sup.-8 Torr or lower, and effecting high frequency induction heating while controlling the partial pressure of each of O.sub.2, H.sub.2, CO in the atmosphere inside the vessel. Further, the vacuum vessel, the metal crucible and an induction heating coil attached to the crucible, each of which has double jacket structure, are heated or cooled by supplying circulating heating or cooling water in a water-passage space of each of the vacuum vessel, the metal crucible and the induction heating coil, so that the inside of the melting furnace is baked.