TECHNOLOGY FOCUS - POLYMERS - Preferred Particles: The water-repellent particles are polytetra fluoroethylene particles, and not fibrillated. Preferred Method: The carbon particles and water-repellent particles are dispersed in water in presence of a non-ionic surfactant and carbon-water repellent particles dispersion liquid is prepared. The dispersion liquid is concentrated using phase-separation phenomenon of non-ionic surfactant. The concentrated product is dried, heat sintered and mixed sintered compact is formed. The mixed sintered compact is pulverized, and porous component sintered coarse grains are obtained. Alternately, the carbon-water repellent particles dispersion liquid is electrodeposited and solid content is precipitated. The solid content is sintered and mixed sintered compact is formed. The mixed sintered compact is pulverized and porous component sintered coarse grains are obtained. The porous component sintered coarse grains are dispersed in a solvent, and porous component sintered coarse grain dispersion liquid is prepared. The dispersion liquid is coated on a base material, dried, hot-pressed and a film is formed. The film is then separated from the base material and gaseous diffusion layer is obtained. Preferred Solvent: The solvent is solvent consisting of alkane hydrocarbon of formula: CnH2n+2, where n is 10-16. Preferred Properties: The average hole diameter of void formed in the gap between carbon particles and/or water-repellent particles is less than the average hole diameter of void formed in the gap between porous component sintered coarse grains. The average hole diameter of void formed between carbon particles and/or water-repellent particles, or small diameter through-holes is 0.2 microns or less, and average hole diameter of void formed between porous component sintered coarse grains or large diameter through-holes is 0.5 microns or less. The water-repellent particles have tensile strength of 10 MPa or more. The porous component sintered coarse grains have average particle diameter of 1-500 microns, tensile strength of more than 20 kgf/cm2 and fracture deformation rate of 20% or less. The gaseous diffusion layer has thickness of 100-200 microns.