As the analysis methods of the electromagnetic field, the finite element method (FEM) and the boundary element method (BEM) are well-known. In this paper, we propose the following method. Firstly, we analyze the investigated region only by the FEM, after that locate the hypothetical boundary properly surrounding the points where we desire the values of B in the homogeneous region. Finally, we calculate B at inner points by the BEM with the values by the FEM as the boundary conditions. Analyzing by the FEM at first, this method is easily applied to the complicated multi-material problems. We adopt several kinds of physical quantities to this method as unknowns, and also show the propriety and advantage of this method by analyzing the simple model.