Disclosed is a gas-diffusion layer used for fuel cells, including: a porous material that includes as main ingredients conductive particles and a polymer resin, wherein said gas-diffusion layer internally possesses pores with a size from 0.01 μm to 0.05 μm, and hollows with a size from 1 μm to 200 μm. Further disclosed is a process for producing a gas-diffusion layer used for fuel cells, including: (i) kneading conductive particles, a polymer resin, a pore-forming agent, a surfactant, and a dispersion solvent; (ii) rolling the mixture obtained in Step (i) to shape said mixture into a sheet; (iii) baking the sheet-shaped mixture to sublime the pore-forming agent, thereby forming hollows therein, and to remove the surfactant and the dispersion solvent; and (iv) further rolling the baked mixture to adjust a thickness of the baked mixture.