NOVELTY - Fuel cell stack (10) comprises many fuel cell modules (40) stacked in a predetermined direction, where each fuel cell module comprises: first and second membrane electrode assemblies, each including electrolyte membrane, and first and second electrodes arranged to sandwich two faces of the electrolyte membrane; a first reactive gas flow path arranged to supply a first reactive gas to the first electrodes; a second reactive gas flow path arranged to supply a second reactive gas to the second electrodes; and a coolant flow path arranged to cool down the second electrodes.    USE - The fuel cell stacks are useful as power sources of moving bodies including ships, boats and vehicles.    ADVANTAGE - The fuel cell stack: does not have a coolant flow path for cooling down the first electrodes, but has the first flow path-forming member located between the first and the second membrane electrode assemblies, thus it is relatively small in size and can be easily installed; and has excellent power generation efficiency.    DETAILED DESCRIPTION - Fuel cell stack (10) comprises many fuel cell modules (40) stacked in a predetermined direction, where each fuel cell module comprises: a first membrane electrode assembly and a second membrane electrode assembly, each including an electrolyte membrane, and a first electrode and a second electrode arranged to sandwich two faces of the electrolyte membrane, where the first membrane electrode assembly and the second membrane electrode assembly are arranged, so that the respective first electrodes are opposed to each other; a first reactive gas flow path arranged to supply a first reactive gas to the first electrodes included in the first and the second membrane electrode assemblies; a second reactive gas flow path arranged to supply a second reactive gas to the second electrodes included in the first and the second membrane electrode assemblies; and a coolant flow path arranged to cool down the second electrodes included in the first and the second membrane electrode assemblies, where the fuel cell stack does not have a coolant flow path for cooling down the first electrodes, but has a first flow path-forming member located between the first and the second membrane electrode assemblies to define the first reactive gas flow path.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of the internal structure of the fuel cell stack.    Fuel cell stack (10)    Insulator (21)    First separator (22)    Second separator (26)    Fuel cell modules (40)