A fuel cell separator of the present invention is provided with a reactant gas flow region (8) including a plurality of straight portions (11) and one or more turn portions (12). At least one of one or more turn portions (12) includes a gas mixing portion (12b), a gas meeting portion (12a), and a gas separating portion (12c). Second rib portions (14) are formed in the gas meeting portion (12a) and the gas separating portion (12c). The second rib portions (14) are formed such that the length of an inner second rib portion (14) is shorter than the length of an outer second rib portion (14) in a direction in which the second rib portions (14) extend. An outermost second rib portion (141) located farthest from a center rib portion (13A) is formed so as to be bent inward toward the center line (131).