Electrolyte membrane-electrode assembly for fuel cell and operation method of fuel cell using the same

With respect to a carbon fiber woven fabric to be used as a gas diffusion layer base material in a polymer electrolyte fuel cell, the surface thereof is smoothed and further optimized such that non-uniform infiltration of a coating for water-repellent-layer formation is inhibited, to provide an electrolyte membrane-electrode assembly suitable for an operation under a high humidification condition. As the gas diffusion layer base material used is a carbon fiber woven fabric, wherein a ratio of the area of gap portions where neither warp thread nor weft thread exists: (10/W-Y)(10/Z-X) to the area of portions where warp thread is crossing weft thread: XY mm is in the range of 1/1500 to 1/5, when the carbon fiber woven fabric has a warp density of Z threads/cm, a weft density of W threads/cm, a warp thickness of X mm and a weft thickness of Y mm.