Effects of grain size and cold rolling degree on shape memory ability and transformation temperature were studied in Fe-35% Mn-6% Si shape memory alloy. Md point of the alloy was determined by variation of yield stress with test temperature. The Md point measured in this way was linearly increased with increasing grain size. Shape memory ability of the alloy was decreased with increasing grain size, showing a minimum value at around $63{mu}m$, and then increased with increasing grain size. From this result, it was concluded that the shape memory ability in the grain size smaller than a critical value is controlled by amount of retained ${gamma}$ and prior ${varepsilon}$ phase, but that the shape memory ability in the grain size greater than the critical value is mainly dominated by grain boundary area in unit volume of parent phase. The shape memory ability was decreased with increasing deformation degree. This was because the ${gamma}$ content being available for the formation of ${varepsilon}$ martensite during bending was decreased with increasing deformation degree.