Separator used in fuel cell and fuel cell

A separator disposed facing a membrane electrode assembly is provided with a separator center area facing a power generation area of the membrane electrode assembly, an outer edge part extending from the separator center area to the outer edge, a first manifold hole and a second manifold hole provided to the outer edge part, a fluid flow channel directed from the first manifold hole toward the second manifold hole via the separator center area, and a gasket for surrounding the external periphery of the fluid flow channel and the first and second manifold holes, the gasket being provide to the outer edge part. The gasket is divided into a first gasket part adjacent to an end part of the separator center area and extending along a side of the end part, and a second gasket part for surrounding the external periphery of the first manifold hole and the second manifold hole. The width of the first gasket part is greater than the width of the second gasket part.