PURPOSE: To recover V of high purity contg. no S together with alkali metals from the slag formed in the refining stage of molten iron by dissolving said slag in an extracting liquid to crystallize alkali metals and adding an oxidizing agent and ammonium chloride thereto.

CONSTITUTION: The slag 1 formed in the desulfurizing and dephosphorizing stage of molten iron is supplied together with circulating liquid 3 of processes to an extracting vessel 4 where impurities removing agents 2 are supplied thereto and the Na2O, V2O5 in the slag 1 are extracted. The filtered extract 11 is fed to a crystallizing tank 13, where the Na in the filtrate 11 is crystallized as NaHCO3 which is separated with a filter 17. Part of the crystallized filtrate is fed as extracting liquid 21 to an oxidizing vessel 24 of a V recovering stage where the S in the liquid is oxidized to sulfuric acid ions by an oxidizing agent 27. After the pH of the liquid is controlled, the liquid is fed into a reacting vessel 32 where NH4Cl is added thereto to allow the V in the liquid to settle as NH4VO3. The liquid is conducted to a filter 34, by which the S is separated as Na2SO4, etc. The filtered NH4VO3 37 is calcined in a calcining furnace 38 to form V2O5, and the NH3 formed simaltaneously is recovered in an NH3 absorbing tower 42.