In designing a bolted joint, it is important to know the force ratio. This force ratio is a factor in the case where a load is applied only in the axial direction. it is not considered when an external bending moment is applied on the assembly. In this paper, it is pointed out that influences of the external bending moment on the increment of the bolt axial force should be taken into consideration. For this purpose, the force ratio for the external bending moment, which is the ratio of the increment of the bolt axial force to the external bending moment, is introduced. Then, in the case where clamped parts are T-flanges the method to find the force ratio for the external bending moment is shown. In order to verify these analytical results, experiments are carried out. Comparing these results, they are in a fairly good agreement.