A fuel cell assembly is provided that includes a plurality of cells. Each cell includes an electrolyte layer (2), a pair of gas diffusion electrode layers (3, 4) interposing the electrolyte layer between them, and a pair of flow distribution plates (5) for defining passages (10, 11) for fuel and oxidizer gases that contact the gas diffusion electrode layers. The electrolyte layer (2) includes a frame (21) with a grid (21a), which has a number of through holes (21b), and electrolyte (22) retained in each of the through holes. Because the electrolyte is not required to be interposed between structural members such as the gas diffusion electrode layers and flow distribution plates, the electrolyte is allowed to expand into the passages for the fuel and oxidizer gases so that no undesirable stresses are produced, and the structural members would not be affected by the expansion of the electrolyte.