In order to claiify the fundamental fatigue strength characteristic of precipitation strengthening type stainless steel: A286, fatigue tests were performed. In the fatigue test, the authors paid attention to the behavior of small fatigue cracks in order to make clear fatigue strength properties more than usual fatigue test. As a result of the fatigue test, the fatigue strength characteristic of A286 became clear as shown below. The crack of a size according to a ciystal grain diameter initiates. The cracks are easy to initiate and propagate by Mode II. The fatigue crack does not become a non-propagating crack. Many cracks initiate and propagate even if the stress is around the fatigue limit. The cracks join together and it becomes a long crack, and fmally results in a failure. This is the reason why the fatigue failures occur even after 10^7 cycles.