Disclosed is a hydrogen separation alloy which is adoptable to a product having a large surface area of a side where hydrogen permeates and which has such a metallographic structure as to improve hydrogen permeability and to improve hydrogen-embrittlement resistance. The hydrogen separation alloy used herein is represented by the compositional formula: Nb100−(α+β)M1αM2β where M1 is at least one element selected from the group consisting of Ti, Zr and Hf; M2 is at least one element selected from the group consisting of Ni, Co, Cr, Fe, Cu and Zn; 10≦α≦60, 10≦β≦50, and α+β≦80. The alloy contains inevitable impurities. And the alloy includes two phases, i.e., an Nb-M1 phase serving as a hydrogen-permeable phase, and a M2-M1 phase serving as a hydrogen-embrittlement-resistant phase. The hydrogen-permeable phase and the hydrogen-embrittlement-resistant phase have an elongated structure resulting from rolling. The hydrogen-permeable phase occupies 35% to 70% of an arbitrary 10 μm×10 μm region in a 50 μm×50 μm observation plane of a cross section of the alloy under an electron microscopic observation, the cross section is taken in a direction of thickness reduced by the rolling and in a direction of rolling and flattening.