A cell unit of a fuel cell includes a first separator, a first membrane electrode assembly, a second separator, a second membrane electrode assembly, and a third separator. Resin connecting sections are provided in the outer circumferential ends of the first separator, the second separator, and the third separator. A coupling pin is molded integrally with the resin connecting section of the first separator. A first hole and a second hole are formed on both sides of the coupling pin for selectively inserting a rebuilt pin into either of the first and second holes. A hole for inserting the coupling pin is formed at the center, and the first hole and the second hole are formed on both sides of the hole, in each of the resin connecting sections of the second and third separators.