Fuel-cell gas dispersion layer, and method for producing same

A fuel-cell gas dispersion layer configured from a porous carbon fiber substrate obtained by binding discontinuous carbon fibers using a carbide, and a porous layer containing at least carbonaceous particles, wherein: a porous layer (A) is disposed on one surface (A) of the porous carbon fiber substrate so as to have an average thickness (t1) of 10-55[mu]m; a porous layer (J) is inserted into the interior of the porous carbon fiber substrate in a manner such that at least a portion thereof is present on the opposite surface (B); the proportion of the cross-sectional area in the thickness direction of openings in the interior of the porous carbon fiber substrate is 5-40%; the proportion of openings in the porous layer (A) and/or the porous layer (J) is 50-85%; the thickness of the porous carbon fiber substrate is 60-300[mu]m; and the bulk density of the porous carbon fiber substrate is 0.20-0.45g/cm3.