Carbon Substrate for Gas Diffusion Layer, Gas Diffusion Layer using the same, and Electrode for Fuel Cell comprising the Gas Diffusion Layer

A carbon substrate for a gas diffusion layer that has a porosity gradient in a thickness direction thereof, a gas diffusion using the carbon substrate, an electrode and a membrane-electrode assembly for a fuel cell that include the gas diffusion layer, and a fuel cell including the membrane-electrode assembly having the gas diffusion layer are provided. The gas diffusion layer has improved water discharge ability and improved bending strength both in the machine direction (MD) and cross-machine direction (CMD).