A seal structure of a fuel cell includes an interrupted back-up disposed at least one of a connecting gas passage and a connecting coolant passage. The back-up located on one side of a separator and a portion of a seal line located on the other side of the separator are disposed such that the back-up and the portion of the seal line are overlapped with each other in a fuel cell stacking direction. The interrupted back-up may be formed in the seal or in the separator.
