Using polyimide Langmuir-Blodgett(LB) films as a tunneling harrier, we fabricated Au/Polyimide/1-layer arachidic acid/Pb structure in order to investigate electron transport properties through a junction. It was found that 9-layer polyimide LB films function as a good tunneling harrier in a study of current-voltage(I-V) chararteristics. And several peaks originating in the vibrational modes of the constituent molecules of 1-layer arachidic acid LB films were clearly observed in d$^2$V/dI$^2$- V corves.