The carbothermic smelting reduction of Nb₂O_5 and successive refining of Nb crude metal were studied by Ar/Ar-H₂plasma arc. The Ar plasma reduction of Nb₂O_5 proceeded rapidly to form 2 N grade Nb metal in 15minutes and the Ar-H₂plasma was very effective to the simultaneous decarburization/deoxidation of Nb crude metal. The mixing ratio of carbon and plasma gas composition were main factors to attain the high purity Nb metal. The solubility product, [wt%C] [wt%0], was shown the minimum value of 0.0017 under the carbon ratio(C/Nb₂O_5) of 5.2 and Ar-20%H₂plasma gas. This results confirmed that the high Nb metal over 3 N grade can be refined from Nb₂O_5, by the one step process using the Ar and Ar-H₂plasma.