Electropolymerization was carried out in order to obtain a bio-based polymer by a simple procedure. Ferulic acid, a component of gramineous plants, was selected for this purpose. A thin polymer film was produced in an organic solvent medium (i.e., CH2Cl2/methanol (4:1 v/v) in the presence of 0.2 M LiClO4), whereas it was not obtained in a totally aqueous medium (0.2 M NaOH). Scanning electron microscopic analysis showed that the polymer film had a porous lamellar structure of ~10 μm thickness. Most of the carboxyl groups remained, and IR spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses revealed that o-quinones existed in the polymer film. After electropolymerization, caffeic acid, sinapic acid, 3,6-bis(4-hydroxy-3-methoxyphenyl)tetrahydrofuro[3,4-c]furan-1,4-dione (1), and 4,4’-dihydroxy-3,3’-dimethoxy-β,β’-bicinnamic acid (2) were detected in the organic reaction medium; this suggested that demethylation, methoxyl group addition, and radical coupling reactions occurred at the electrode surface.