In this paper, the authors propose a method for analyzing the permeance distribution of rotating machines. The proposed method enables consideration of the nonlinear characteristics of iron cores with regard to magnetic saturation. In representing the nonlinear characteristics, the relation between flux density and magnetomotive force is approximated by a power series. Variations in permeance caused by magnetic saturation are calculated by the harmonic balance method. The analytical results demonstrate the capability of the method for qualitative analysis of the saturable higher harmonic characteristics of rotating machines.