A separator for a fuel cell is provided and may include a plurality of linearly extending protrusions and a plurality of flat walls alternately arranged with the plurality of linearly extending protrusions. Each protrusion is defined by a top wall and a pair of side walls and the linearly extending protrusions are parallel to each other. In addition, a gas passage forming groove is defined between each adjacent pair of linearly extending protrusions, a belt-like groove is provided on an inner surface of each flat wall that faces the corresponding gas passage forming groove, and an inclination angle is set with respect to each flat wall and corresponding side walls.