A fuel cell includes a membrane electrode assembly, and a first and second separators for sandwiching the membrane electrode assembly. The first separator has an oxygen-containing gas flow passage for allowing an oxygen-containing gas in a serpentine pattern to flow horizontally back and forth, and flow downwardly. Partition areas are provided along the oxygen-containing gas flow passage in the serpentine pattern. The partition areas are formed by partially cutting out a gas diffusion layer. Insulating seals for preventing leakage of the oxygen-containing gas are provided in the partition areas.