A break junction method using a scanning tunneling microscope has been applied to electrical conductance measurement of newly designed oligothiophene molecules terminated with a thiocyanate group. The tunneling conduction was evident from an exponential decay of the conductance as a function of the molecular length up to ca. 6 nm. The tunneling decay constant was estimated to be 0.1 A (-1). The pre-exponential factor was 1.3 x 10 (-6) S, which was smaller than that observed for alkanedithiols.