To provide a refining method by which, at the time of separating impurities such as magnesium chloride and metallic magnesium remaining in a sponge titanium at high temperature under the reduced pressure, introducing the impurities into a capacitor vessel and performing condensation, thereby separating the same away, a separating vessel is not deformed, and to provide a vacuum separating device.

In this refining method in which, as for the sponge titanium obtained by bringing metallic magnesium into reaction with titanium tetrachloride in a separating vessel 5 contained in a heating furnace, impuritis are removed under a reduced pressure, the pressure in the heating furnace 1 and the separating vessel 5 is reduced, and furthere, in the process of the pressure reduction, the pressure in the separating vessel 5 is made the same as that in a space part 1a between the separating vessel 5 and the heating furnace 1 or higher than that.