Nanometer-scale hole- and bit-modifications were successfully performed by applying the local electric field of scanning tunneling microscope (STM) to an oligosilane-langmuir-Blodgett (LB) film composed of a tridecamethylhexasilanylacetic acid (MeSi(6)AA) and a stearic acid-LB film. It has been found possible to perform these modifications on the monolayer with several tens nanometer-scale resolution by halting the probe tip and applying a higher bias voltage than used for usual STM imaging. Each modification could be selected by changing the polarity and the bias voltage applied. Examination of hole- and bit-formation conditions has suggested that the electron beam emitted from the tip under a high electric field makes the hole modification, and that chemical oxidation or reduction of the concerning molecule results in the bit modification.