Discontinuous parts of steel structure, such as ship construction may be subjected to stress-es exceeding yield point which cause plastic deformations and cracks on occasion due to over loads arisen from waves etc.. To make clear the strength of such structure, the elasto-plastic analysis by means of finite element method is often employed. For one half cycle loading analysis, the method of Yamada et al. is well known as adequate one for practical application. However the method of analysis based on three dimensional stress-strain law of a material which is able to simulate its behavior including the effect of arbitrarily varied loading cycles taking Baushinger effect into account has scarcely been proposed. Authors present a method of analysis which deals with such objects, using an anisotropic hardening model by means of yield surface theory to obtain the constitutive equation, employing a simulation algorithm developed by one of the authors et al. for uniaxial loading which is capable to predict the stress-strain behavior of steel subjected to arbitrarily varied loading cycles. This method was applied to the analyses for ductile fracture problem and the prediction of plastic fatigue endurance of steel structures.