Property changes and microstructural evolution of deformed and subsequently annealed austenitic stainless steel are investigated. SUS304 samples were deformed by high pressure torsion to obtain 100 % alpha' volume fraction. When plastically deformed SUS304 is annealed in the temperature range of 200-600 A degrees C for 1 h, peak maxima in hardness, electrical resistivity, and saturation magnetization appears at 400 A degrees C. In this study, SUS304 containing 100 % alpha' was investigated on the basis of changes in microstructure and mechanical properties after annealing at the temperature of 400 A degrees C for up to 500 h. The observed property changes are attributed to solute segregation, strain relaxation, and G phase precipitation.