Disclosed is a fuel cell (1) configured from a laminated body comprising separators (2) and a membrane electrode assembly (3), which is equipped with an anode electrode layer and a cathode electrode layer located on opposite surfaces of an electrolyte membrane (7). The separators (2) and the membrane electrode assembly (3) have a substantially rectangular shape. The separators (2) are equipped with a smooth surface or flow channels and the electrode layers are formed from a gas diffusion layer and a catalyst layer. The aspect ratio (R) of the length of the flow channel to the width of the flow channel (flow channel length/flow channel width) on the anode side or the cathode side of the membrane electrode assembly (3) is 0.01 or more, and less than 2. Furthermore, the equivalent diameter (D) (mm) of the flow channels or the gas diffusion layer in the horizontal direction satisfies general formula (1): D=B×(R×Acat)1/3... where Acat is the catalytic surface area (cm) of the membrane electrode assembly (3), and B is an constant in the range of 0.005 - 0.2 inclusive.
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