Redox ions are deposited on a polyelectrolyte-coated gold electrode by an electric field to fabricate an ion-selective thin film electrode. The Fe(CN) ions are deposited on a few monolayer-coated polyelectrolyte gold electrode by a slow periodic potential cycle. The deposition process and electrode properties are quantitatively and simultaneously monitored by cyclic voltammetry and a novel technique, using a Scanning Electrometer for Electrical Double-layers (SEED). No redox properties are obtained without the electric-field-deposition. Owing to the redox mediation and net charge due to the redox ion, the electrode is ion-selective. We demonstrate the principle to detect 1 µM of dopamine in a mixture with 1 mM of ascorbic acid.