We have studied the electrical conductance of the single 1,2-ethanedithiol molecular junction prepared in ultrahigh vacuum (UHV). The single molecular junction was fabricated by breaking the Au contacts with mechanically controllable break junction technique in the presence of 1,2-ethanedithiol. The conductance of the single 1,2-ethanedithiol molecular junction was 0.13 G(0) (2e(2)/h), larger than the value expected for the single molecular junction fabricated in the molecular solution. The present study revealed that the molecular junctions created in UHV exhibited lower contact resistances due to the clean vacuum environment.