NOVELTY - The cell (11) has a separator (28) provided for sandwiching electrolyte electrode assemblies (26). A fuel gas channel (46) is provided along a surface of the separator and a groove (54a) is formed in the separator. A mesh unit (64) releases stress that is applied to an electrolyte and a cathode. A fuel gas supply unit is provided hermetically at a center of an exhaust gas channel, where fuel gas supplied from a fuel gas inlet is diffused from the center of an anode. The assemblies are arranged along a virtual circle concentric with the separator.    USE - Used in a fuel cell system that is utilized in stationary and mobile applications, and in a vehicle.    ADVANTAGE - The groove is formed in the separator to reduce thickness of the separator so reducing dimension of the fuel cell in the stacking direction to greatly simplify a structure of the separator, to fabricate the cell in an economic manner and achieve reduction in production cost of the separator. The electrolyte electrode assemblies are arranged along the virtual circle concentric with the separator to reduce overall size of the fuel cell and avoid influence of the heat distortion in the fuel cell. The mesh unit releases the stress that is applied to the electrolyte and the cathode so reducing the damage at the time of stacking the fuel cell and achieving improvement in the performance of collecting electricity from the fuel cell. The fuel gas supplied from the fuel gas inlet is diffused from the center of the anode such that a uniform reaction occurs smoothly so achieving improvement in fuel utilization ratio in the cell. The fuel gas supply unit is provided hermetically at the center of the exhaust gas channel so eliminating the need of the fuel cell to consume fuel gas unnecessarily, while preventing the fuel gas and the exhaust gas from being mixed together, and hence achieving improvement in the heat efficiency of the fuel cell.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a fuel cell stack formed by stacking a set of fuel cells.    DESCRIPTION OF DRAWING(S) - The drawing shows a fuel cell system.    Fuel cell (11)    Cathode (22)    Anode (24)    Electrolyte electrode assemblies (26)    separator (28)    Fuel gas inlet (38)    Fuel gas channel (46)    Protrusion (48)    Fuel gas supply channel (54)    Groove (54a)    Oxygen-containing gas channel (62)    mesh unit (64)    Oxygen-containing gas supply unit (67)