An object of the present invention is to provide a gas diffusion layer having gas flow passages formed at its one main surface, which is capable of achieving a further improvement in power generation performance. The fuel cell-use gas diffusion layer (14A, 14C) of the present invention has a double-layer structure made up of a first diffusion layer (15A, 15C) having gas flow passages (21A, 21C) at its one main surface, and a second diffusion layer (16A, 16C) disposed on the other main surface of the first diffusion layer. The first diffusion layer and the second diffusion layer are each structured with a porous member mainly comprised of conductive particles and a polymer resin, and the first diffusion layer is structured to be lower in porosity than the second diffusion layer.