In general, when geometry and current distribution have a periodic or symmetric property, the analysis of a part model is sufficient to represent that of a whole model by using the periodic boundary condition. It is impossible, however, to apply the periodic boundary condition when the current distribution is not symmetric even if the geometry of the model is symmetric. In this paper, a novel technique to resolve this problem is proposed. Even when the geometry is symmetric and the current distribution is not, the proposed method enables that calculation time for a whole model is reduced to that for a part model. The proposed method is applied to a deflection yoke (DY), and validness and efficiency of the method are verified.