An inner electrode for barrier film formation is an inner electrode for barrier film formation that is inserted inside a plastic container having an opening, supplies a medium gas to the inside of the plastic container, and supplies high frequency power to an outer electrode arranged outside the plastic container, thereby generating discharge plasma on the inner surface of the plastic container to form a barrier film on the inner surface of the plastic container, and that is provided with a gas supply pipe having a gas flow path to supply a medium gas and an insulating member screwed into an end portion of the gas supply pipe to be flush therewith and having a gas outlet communicated with the gas flow path.