The purpose of this paper is to propose a practical mean strength formula and a variation formula for H-shaped steel beams as functions of the slenderness ratio, initial deflection, and residual stress. The finite element method was employed for calculating elastic-plastic behavior under monotonic loading with consideration of the randomness of material properties such as yield strength, maximum strength, and strain at starting strain hardening. The statistics of the member strength were obtained by Monte Carlo simulation. The mean values of the yield strength of H-shaped steel beams can be formulated as Eq. (20), and the coefficient of variation of the yield strength is formulated as Eq. (30). The mean value of the maximum strength of H-shaped steel beams can be formulated as Eq.(26), and the coefficient of variation of the maximum strength is formulated as Eq. (31).