Austenitic stainless steel is more or less difficult with conventional gas nitriding treatment, but it can be nitrided after appropriate pre-heat treatment. The pretreatment was more effective upon nitriding for austenitic stainless steel than martensitic stainless steel. Both thickness and microhardness measurements indicated that effect of the nitriding treatment was more sensitive in austenitic stainless steel than martensitic stainless steel with nitriding time. Fatigue strength was most increased with SACM 645 steel among three steels.