Abstract: A method is provided for producing a coating layer for an exhaust gas purification catalyst device that can inhibit detachment of the coating layer when the coating layer is formed on the exhaust gas purification catalyst device. The method comprises covering a substrate with a slurry that comprises carrier particles and a dispersing medium, to form a slurry layer on the substrate, and drying and firing the slurry layer to form a coating layer, wherein the carrier particles have a median diameter (D50) of 4.00 ?m or smaller, the dispersing medium comprises water and a water-soluble alcohol, and the amount of the water-soluble alcohol in the slurry is 0.50 mass % to 12.00 mass % with respect to the slurry.