A fuel cell stack FS includes: a stack A that includes a single cells C that are stacked, each of the single cells including a frame 2 that holds an outer periphery of a membrane electrode assembly 1 and a pair of separators 3, 4 sandwiching the membrane electrode assembly 1 and the frame 2; and a case 50 that houses the stack A. The frame 2 comprises a protrusion 11 that protrudes outward from an outer periphery of a frame body 2A beyond an outer peripheral edge of the pair of separators 3, 4. A protrusion length of the protrusion 11 is greater than at least a gap between the frame 2 and one of the pair of separators 3, 4, and the protrusion 11 is bendable with respect to the frame body 2A. The protrusions prevent a contact between the separators 3, 4 of the single cell C and a contact between the end faces of the separators 3, 4 and the case 50 so as to prevent a short circuit of the single cell C.