A fuel cell stack includes a stacked body, a negative and positive terminal plates stacked on opposite ends of the stacked body, insulators disposed outside the terminal plates, and the end plates disposed outside the end plates. The insulator includes a first insulator plate, a second insulator plate, and a third insulator plate. Bypass passages are formed on the first insulator plate and the third insulator plate for discharging water in an oxygen-containing gas and water in a fuel gas.