Gas diffusion member, gas diffusion unit, and fuel cell

A gas diffusion member which can reduce internal resistance of a fuel cell. A gas diffusion member arranged between a separator and a catalyst layer of a fuel cell, including: a porous material layer; and a conductive material layer; wherein: the porous material layer is formed of a conductive porous material; the conductive material layer is formed of a conductive material; and the conductive material layer is arranged on a surface of the porous material layer on a side of the separator and is provided so that pores of the porous material layer are filled with the conductive material.