A cell unit (12) of a fuel cell (10) includes a first membrane electrode assembly (14), a first metal separator (16), a second membrane electrode assembly (18), and a second metal separator (20). Frames (28a, 28b) are provided at outer circumferences of the first and second membrane electrode assemblies (14, 18). An oxygen-containing gas supply passage (32a) and a fuel gas supply passage (30b), and an oxygen-containing gas discharge passage (30b) and a fuel gas discharge passage (32b) are provided in one pair of opposite sides of the frames (28a, 28b), and a pair of coolant supply passages (34a) and a pair of coolant discharge passages (34b) are provided in the other pair of opposite sides of the frames (28a, 28b) at distances from one another.