An apparatus for purifying sodium metal including: a top flange, a transparent slice, a hollow flange, a vacuum distillation kettle, gaskets, and bolts. With this apparatus, solid sodium is liquefied by heating. The volatile impurities contained in the liquid sodium metal evaporate out of the vacuum pump. After heating the liquid sodium to a high temperature, circulating cooling water is added to the condenser tube by radiation-auxiliary distillation. High-purity argon is then added to remove volatile impurities, and thermal radiation is performed to accelerate the evaporation rate at the surface of the liquid sodium. Consequently, gaseous sodium rapidly condenses on the condenser tube and becomes solid sodium.