Fuel cells and methods of operating same are provided. In an embodiment, fuel cells include cylinders each provided with a spiral form groove portion in the surface thereof and disposed in air supply or exhaust pipes are rotated, wherein the amount of air supplied to power generation cells can be sequentially increased on a cell-by-cell basis, and water formed at the power generation cells can be discharged by sequentially raising the pressure of air. In this regard, each power generation cell is constantly supplied with not less than a fixed quantity of air, thus stable power generation can be achieved.