Polyvinyl alcohol gel (PVA gel) has been applied in various fields as a biomedical material in Japan since the mechanical and the electrical characteristics are very similar to the human body. In this paper, the electrical characteristics of the electrode coated with PVA gel containing saline solution are described. The electrode has been applied to a stimulation electrode in an extracochlear prosthesis. It is expected that the coated electrode can stick to the round window membrane without scarring it. From the experimental results, is was found that the electrical impedance of a stimulation electrode coated with PVA gel exhibited good stability and the effective double-layer capacitance of the coated electrode was less dependent on the current than the capacitance of the Pt-Ir electrode. The electrical characteristics of the PVA electrode were proved to be very stable for long term use in-vivo. The coated electrode was ascertained to be able stimulate reliably the auditory nerves of a guinea pig.