NOVELTY - High temperature/high pressure processing of ink containing carbon particles (2) in which the catalyst is supported, a primary ion conductive polymer electrolyte (27) and a solvent, and the polymer electrolyte is introduced into the pore in the carbon particles, and primary pore (5) in primary aggregate (4) of carbon particles. The product is cooled and vacuum-dried to obtain composite particles. An electrode catalyst ink is obtained by adding secondary ion conductive polymer electrolyte (28) and solvent to composite particles, and an electrode catalyst layer is formed using the ink.    USE - Manufacture of electrode catalyst layer for polymer electrolyte fuel cell (claimed). Uses include but are not limited to power supply for electric vehicle, motor vehicle, electric vehicle, notebook personal computer, mobile telephone, portable information terminal, domestic electric power generation apparatus, etc.    ADVANTAGE - The electrode catalyst layer is manufactured with high water retention property and utilization factor of catalyst, and favorable gas permeability.    DETAILED DESCRIPTION - High temperature/high pressure processing of ink containing carbon particles in which the catalyst is supported, a primary ion conductive polymer electrolyte and a solvent, and the polymer electrolyte is introduced into the pore in the carbon particles, and primary pore in aggregate of carbon particles. The resulting product is cooled and vacuum-dried to obtain composite particles. An electrode catalyst ink is obtained by adding a secondary ion conductive polymer electrolyte and solvent to composite particles. An electrode catalyst layer is formed using the catalyst ink. The acid value of primary ion conductive polymer electrolyte is less than that of secondary ion conductive polymer electrolyte. An INDEPENDENT CLAIM is included for polymer electrolyte fuel cell, which has a membrane electrode assembly provided with pair of electrode catalyst layer in which polymer electrolyte membrane is clamped, a pair of gas diffusion layer which clamps the membrane electrode assembly, and a pair of separator which clamps the membrane electrode assembly and gas diffusion layer.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of electrode catalyst layer.    Catalyst particles (2)    Primary aggregate (4)    Primary pore (5)    Primary ion conductive polymer electrolyte (27)    Secondary ion conductive polymer electrolyte (28)