Aminophenanthroline derivatives are investigated as the unique monomer of organic polymeric material showing electrochromic behavior, because they have large π-electron conjugated system and hetero atoms in their unit structures. Electropolymerization technique is applied to preparing electroactive thin film on the electrode with these monomers. Especially, from (5-aminophenanthroline) ruthenium complex, electroactive yellow thin film is obtained on Pt or ITO electrode. This film shows electrochromic behavior of which yellow thin film is decolorized by applying the oxidative potential to the film. This behavior is considered to be arisen from the changes in the electronic structure of Ru-aminophenanthroline complex, which are caused by the redox between Ru²⁺ and Ru³⁺.