PURPOSE: To increase the efficiency of removal of MgCl2 when a refractory metal contg. Mg and MgCl2 is heated to vaporize the Mg and MgCl2, which are then solidified by cooling, by extending a cooling surface when the partial pressure of Mg lowers remarkably.

CONSTITUTION: A refractory metal contg. Mg and MgCl2 is put in a reduction reactor 4, the reactor 4 is evacuated through a duct 14 for evacuation, the lower part of a retort 3 is heated to about 950W1,000°C with an electric furnace 2, and a cooling agent is passed through a main jacket 8 on the retort 3. Mg and MgCl2 are vaporized from the refractory metal in the reactor 4 by heating, and they enter a reactor 7, solidify and deposit on the cooling surface. In the latter half of the separating stage in which the partial pressure of Mg lowers remarkably, the cooling agent is further passed through a secondary jacket 9 to extend the cooling surface. Thus, the efficiency of capturing of MgCl2 is chiefly increased.