Nanometer-scale measurements of the physical properties of materials are needed in nano-electronics. We constructed a new probing system, a dual-probe scanning tunneling microscope (D-STM) with two STM probes. The D-STM permits us to measure the current-voltage curves of a single nanotube ring (20−100 nm in diameter). We found that we could make the nanotube ring behave as a transistor. However, the D-STM we constructed cannot be applied to insulators, since the instrument used a conventional tunneling current response circuit. Then, we developed a triple-probe atomic force microscope (T-AFM) with three electric probes that could be connect to the samples. Using T-AFM, we have measured a three-terminal single molecule DNA device. These results suggest that there are possibilities of developing nanometer-scaled electronics circuits.