The routings in an analog PCB (printed circuit board) mainly consist of non-rectilinear and curved lines, which significantly affect the characteristics of an electric circuit. So, a building automatic design system for an analog PCB is still regarded as a difficult problem. In this paper, a new method for modelization of PCBs is proposed, replacing the wiring and the boundary on a PCB with surface charges, and a new routing searching method satisfying the condition of minimization of the total potential energy in all regions of a PCB. Also the applicability to an analog PCB wiring design is shown. From the basic study using computer simulation, it is found that a routing searched by this method is quite similar to the Steiner tree. In the end, it is shown that this routing can be searched by the steepest descent technique.