The plasmon-induced photo-polymerization of molecules was observed at the gold nano structures on TiO₂ electrodes in an electrolyte. Spatially confined electromagnetic fields generated by the excitation of localized surface plasmon resonance leads to highly localized deposition of conductive polymer at the edge of Au nanostructures on TiO₂ electrodes. Characteristics on the deposition rate depending on the Au nanostructures provide the information on the mechanism of plasmon-exciton conversions.