Gas diffusion member, gas diffusion unit, and fuel cell

A gas diffusion unit comprising a gas diffusion member and a separator, wherein the gas diffusion member is adapted to be arranged between the separator and a catalyst layer of a fuel cell, the gas diffusion member comprising:

• 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;
• 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 are filled with the conductive material;
• the gas diffusion member is adhered to the separator via the conductive material;
• and
• a thickness of a part of the conductive material layer formed inside the porous material layer is defined as T1 and the thickness of the part formed outside the porous material layer is defined as T2, and a value T2/T1 is 0.5 or less.