NOVELTY - Slurry (10) containing electrical-conductivity substance and destruction-by-fire material (M) is fed to solid-liquid separation. Solid content is accumulated, and liquid is fed to papermaking process to obtain sheet. Material (M) in paper-made sheet is heat-processed and burned down, and pore is increased in sheet to obtain gaseous-diffusion component. Slurry in slurry preparation process contains resin fiber burned down from sheet by heat processing. Resin fiber on paper-made sheet is burned down from sheet by heat-processing in pore formation process.    USE - For manufacturing gaseous-diffusion component for fuel cell such as solid polymer electrolyte fuel cell.    ADVANTAGE - The gaseous-diffusion component having improved reliability, electroconductivity and gas permeability is manufactured, by reducing compounding quantity of destruction-by-fire material such as wood pulp.    DETAILED DESCRIPTION - Slurry (10), which uses electrical-conductivity substance having electroconductivity and destruction-by-fire material burned down by heat processing, as a basic component is prepared. The slurry is subjected to solid-liquid separation. The solid content is accumulated, and papermaking process is performed with respect to the liquid, to obtain a sheet essentially containing electrical-conductivity substance and destruction-by-fire material. The destruction-by-fire material contained in paper-made sheet is burned down by heat processing, and pore is increased in the sheet to obtain gaseous-diffusion component having gaseous-diffusion property. Slurry in the slurry preparation process contains resin fiber burned down from the sheet by heat processing. The resin fiber on the paper-made sheet is burned down from the sheet by heat-processing in pore formation process. INDEPENDENT CLAIMS are included for the following:    (1) manufacture of gaseous-diffusion raw material; and    (2) gaseous-diffusion raw material.    DESCRIPTION OF DRAWING(S) - The figure shows the block diagram explaining the mixing process of carbon fiber, pulp and resin fiber during formation of papermaking slurry. (Drawing includes non-English language text)    Slurry (10)