ELECTRODE CATALYST LAYER AND POLYMER ELECTROLYTE FUEL CELL

Provided are an electrode catalyst layer for a polymer electrolyte fuel cell, which is capable of improving drainage property and gas diffusion properties and capable of high output, and a polymer electrolyte fuel cell provided with the same. An electrode catalyst layer () bonded to a polymer electrolyte membrane () includes a catalyst (), carbon particles (), a polymer electrolyte () and fibrous material (), in which the electrode catalyst layer () has a density falling within a range of 500 mg/cmto 900 mg/cm, or has a density falling within a range of 400 mg/cmto 1000 mg/cm, and the mass of the polymer electrolyte () falls within a range of 10 mass % to 200 mass % with respect to the total mass of the carbon particles () and the fibrous material ().