A carbon substrate for a gas diffusion layer of a fuel cell, the carbon substrate being a porous carbon substrate having a first surface and a second surface opposite the first surface, the carbon substrate includes a plurality of carbon fibers arranged irregularly to form a non-woven type and a carbide of an organic polymer located between the carbon fibers to bind the carbon fibers to each other, the carbide has a graphite structure, and the carbon substrate has a Bragg diffraction angle 2θ of less than 26.435° and a interplanar distance d(002) of less than 3.372 Å, a gas diffusion layer employing the same, an electrode for a fuel cell, a membrane electrode assembly for a fuel cell, and a fuel cell. When the gas diffusion layer is manufactured using the carbon substrate according to the present disclosure, cell voltage characteristics of the fuel cell may be greatly improved.