The purposes of this study are to clarify effects of Fe. Mn alloying on microstructure and ductility of the NiAl base shape memory alloys. It has been found that the γ phase formed by the alloying Fe or Fe+Mn has a drastic effect not only on the hot workability but also on the tensile ductility at room temperature. The enhancement in ductility is mainly due to presence of the γ phase with a high ductility and grain refinement of the β phase by the adjacent γ phase for annealing. The specimens quenched from 1300℃ consisted of the β′(L1_0) and r(disorded fcc). The β′ martenste have a {111} $lt;112$gt; internal twins. The c/a value of the β′ phase is 0.86-0.87, almost equal to that of the binary Ni-Al β′ phase. And the lattice parameter of the γ phase is 0.358-0.359㎚.