The atomic structure and its electric conductance of the Pt nano contact in a benzene atmosphere were investigated. The conductance, shot noise, and conductance fluctuation measurements revealed the number of the molecules bridging between Pt electrodes. The vibration spectroscopy of single molecule junction and isotopic shift in vibration spectroscopy confirmed the bridging of the benzene molecule. We could determine the atomic structure of the single benzene molecule junction and its conductance around 1 G₀(2e²/h). Highly conductive single molecule junction could be fabricated by direct biding of π conjugated benzene molecule to metal electrodes. In addition, we could fabricate single molecule junctions showing high and fixed conductance values, by using Ag as electrodes or C₆₀ as molecules.