A fuel cell includes a reaction layer including: a membrane electrode assembly (MEA); and gas diffusion layers (GDLs) each of which is disposed at both side surfaces of the MEA. A porous separation layer has one surface adhered to one surface of the reaction layer and supplied with reaction gas, and a cathode bipolar plate has a panel shape and adhered to another surface of the porous separation layer. A front end part of the cathode bipolar plate having a manifold that is supplied with the reaction gas and having a plurality of diffusion channels through which the reaction gas directs from the manifold toward the porous separation layer. The cathode bipolar plate has a partition wall channel which separates the porous separation layer, which extends in a direction in which the reaction gas flows, and which extends from the manifold in a diagonal direction.