Shrinkage and deformation of a seal member are suppressed. In a separator (20 (20a-20d)), at least uneven shapes for forming a flow channel for a fluid are in an inverted relationship on the front and the rear surfaces, and a manifold (16b) for supplying and discharging the fluid is formed. When a seal member (13c) for sealing the fluid along the periphery (20e) of the separator (20) forming the outline of the manifold (16b) is arranged, a protruding section (21), which can function as a spacer between the separator (20) and other member adjacent to the separator , is arranged between the seal member (13c) and the periphery (20e).