We have developed a novel proton-conduction film by recasting an aqueous solution comprising an acid polymer and a base polymer. This technique is called the polyelectrolyte complex method, in which a film is generally formed by using a concentrated acidic solution, because it is hard to obtain a stable one from a neutral solution. First, poly (sodium-p-stylenesulfonate) (PSSNa) was partially changed to a proton form (PSS) by using cation exchange polymer beads prior to the blending with polyethyleneimine (PEI). By using thus-prepared neutral aqueous blend solution, it has been possible to prepare a stable polyelectrolyte complex film that demonstrates a higher ionic conductivity than that of Nafion. This report also describes ionic conductivity dependence on a SS/EI mole ratio and acid-activation processes of the film.