GAS DIFFUSION LAYER, ELECTRODE FOR FUEL CELL, MEMBRANE ELECTRODE JUNCTION, AND FUEL CELL

A gas diffusion layer comprises a gas diffusion substrate having a first surface and a second surface formed opposite to the first surface; and a microporous layer containing a conductive powder and disposed on the first surface of the gas diffusion substrate and in the gas diffusion substrate, wherein the microporous layer is continuous in a thickness direction of the gas diffusion substrate, an amount of the microporous layer on a cross section perpendicular to the thickness direction is maximum at a first cross-sectional position in the thickness direction and decreases from the first cross-sectional position toward the second surface, an amount of the microporous layer included in a region on the first surface side of a central position of the gas diffusion substrate in the thickness direction is 80% or more of an amount of the entire microporous layer, and the microporous layer extends to the second surface.