Application of performance-based design, which is promoted as an international trend that is representative of ISO2394, emphasizes the importance of evaluating structural safety based on the reliability design method. This paper describes an effect of return period and its variation of input ground motions on partial safety factors for use of the reliability design method for steel rigid-frame piers. For this study, seismic hazard assessment was evaluated from the probabilistic seismic hazard data. Then, partial safety factors are calculated using AFOSM. The results show that the consideration of the variation of the seismic load in each site is necessary to evaluate the optimum partial safety factors against the objective reliability index. Therefore, the effect of the return period and its variation of input ground acceleration is confirmed by the trail design of a steel rigid frame pier to withstand the local buckling against ground excitation.