An extremely thin fluorinated polyethylene (FPE) film was prepared on a carbon black (CB) surface and the properties were studied. It was found that polyethylene as the precursor can cover the whole surface of the CB particles with a thin film different from the conventional Teflon dispersion (PTFE), and it can be fluorinated easily to produce a Teflon-like hydrophobic material. The resulting FPE/CB material showed a distinctive hydrophobic property and a comparable thermal stability compared with PTFE under the operating conditions for phosphoric acid fuel cells (PAFCs). An advanced gas diffusion electrode for PAFCs is proposed in which a new design concept of the electrode structure is applied where the functions of electrolyte network and gas network are assigned completely to catalyzed CB and FPE/CB. The cathode optimized in the structure with the new FPE/CB exhibited a high performance for oxygen reduction compared with cathodes using conventional PTFE owing to the improved catalyst utilization and gas permeability, and showed a potential for long operational life owing to less performance degradation resulting from the prevention of flooding of the gas network with electrolyte during operation.