A porous base material and a porous electrode having both gas permeability suitable for a gas diffusion layer for a fuel cell vehicle and mechanical strength capable of withstanding continuous processing in a roll-to-roll manner, and a porous electrode which is suitable for an electrode for a redox flow cell and has excellent diffusibility of an electrolyte are required. Provided is a porous base material containing a carbon fiber (A) having an average fiber diameter of 10 to 20 μm, an average fiber length of 2 to 30 mm, a tensile modulus of elasticity of 200 to 600 GPa, and a tensile strength of 3,000 to 7,000 MPa and a carbon binder (D), in which the carbon fiber (A) is bound with the carbon binder (D).