In a fuel cell assembly with at least one cell including an electrolyte layer, a pair of gas diffusion electrode layers interposing said electrolyte layer between them, and a pair of flow distribution plates (5) for defining passages (10, 11) for fuel and oxidizer gases that contact said gas diffusion electrode layers, a heater 62 and various sensors (61a, 61b and 61c) are formed on at least one of the flow distribution plates so that the work needed for installing the heater and sensors is simplified. By embedding them in a substrate, the need for a complex sealing arrangement can be eliminated. In particular, if each flow distribution plate is formed by performing an etching process on a substrate, and forming the heater and sensors in succession to the step of forming each flow distribution plate, the installation of sensors and fabrication of the fuel call are simplified.