Tensile and fatigue properties of stainless steels exposed to highly pressurized hydrogen gaseous environment are investigated using small specimen. The hydrogen content distribution in the small specimen is nearly uniform, because the thickness of the specimen is very small (0.3mm). Metastable austenitic stainless steel SUS304 and SUS304L show the degradation of tensile ductility and the fatigue life by exposure to hydrogen gas environment. Even stable austenitic stainless steel SUS316L shows the little degradation of the tensile ductility in the high hydrogen content range, but doesn't show the degradation of the fatigue life.
