A fuel cell includes a separator having an uneven shape integrally formed on the front and the back surfaces thereof, so that gas can flow in a recessed portion of one surface and cooling water can flow in a recessed portion of the other surface. The separator has a gas passage portion connected to a manifold via a gas outlet/inlet portion. A first continuous portion that connects the gas outlet/inlet portion to the manifold is different from a second continuous portion that connects the gas outlet/inlet portion to the gas passage in communicating width. The gas outlet/inlet portion has an elliptical embossed portion that protrudes toward the gas passage side. A major axis direction of the embossed portion inclines relative to a straight axis connecting one end of the first continuous portion and one end of the second continuous portion toward a straight axis connecting the other ends of the first and second continuous portions.