A fuel cell stack includes a first metal separator and a second metal separator sandwiching a membrane electrode assembly. Bead seals are provided on the first and second metal separators. The bead seals protrude toward the membrane electrode assembly. A seal member is provided on a top part of each of the bead seals. In the process of producing the fuel cell stack, pressure medium is supplied to a coolant flow field formed between the first metal separator and the second metal separator. The supply pressure of the pressure medium is set to not less than the supply pressure of a coolant supplied to the coolant flow field during normal operation of the fuel cell stack.