The purpose of this paper is to clarify the statistical properties of member ductility requested to ensure the deformation capacity of steel moment resisting frames considering the uncertainty of member ductility. The drift angles at three different limit states are defined as the deformation capacity. Two types of steel moment resisting frames with the different number of stories are used as analytical frame models. Two types of member restoring force-deformation characteristics are employed in the analytical models. For the analytical models, the load-deformation relations under static horizontal loads are calculated using Monte Carlo simulation and pushover analysis with considering stress-redistribution. Based on the analytical results, this paper proposes relationships between the mean value and the coefficient of variation of member ductility to ensure the deformation capacity.