Fuel cell stack with cooling cells

A fuel cell stack 10 comprises a power-generating cell 12 and a cooling cell 18 which are stacked, an insulating means 68 for electrically insulating the cooling medium supplied into the cooling cell 18 from the power-generating cell 12, and a conducting means 70 for electrically connecting the power-generating cells 12 arranged with the cooling cell 18 interposed therebetween to one another. Accordingly, the earth fault and the liquid junction, which would be otherwise caused by cooling medium, is reliably avoided with a simple structure, making it possible to maintain desired power generation performance.