The Fe-Mn-Si shape memory alloy was first found by Sato et al. Since then, a large number of studies about the addition of other alloying elements to the alloy, for the purpose of improvement of its corrosion resistance and shape memory effect, have been made. Most of them have used the alloy systems consisting of single {gamma} phase at room temperature. This suggests that, if {epsilon} martensite is mixed with {gamma}, the SME will be deteriorated by it. Therefore, in this study, whether the presence of {epsilon} martensite deteriorates the SME or not was investigated for the Fe-17% Mn alloy. For this investigation, the {epsilon} martensite contents of this alloy were varied in a wide range of 32 to 93 vol.% by a thermal cycling treatment and by a austenitic thermal stabilization treatment.