When an evaluation point shows plasticity, for instance, simplified elastic-plastic analysis can be applied in accordance with the JSME Design and Construction Code (Division 1, Light Water Reactor Code). However this method is known as conservative and elastic-plastic analysis with cyclic stress-strain relation should be performed to obtain an accurate fatigue usage factor. Therefore cyclic stress-strain relation has been developed for austenitic stainless steels. Cyclic stress-strain data were collected from several Japanese reports. Two types of relationship were employed. One is power law type and the other is Ramberg-Osgood type. Those relationships were converted to bilinear type relationships with considering appropriate margin.