Manufacturing method for exhaust gas purification device

The purpose of the present invention is to provide a manufacturing method for an exhaust gas purification device that can uniformly coat a honeycomb substrate with slurry even when using a low viscosity slurry. The present invention pertains to a manufacturing method for an exhaust gas purification device that includes providing a slurry for catalyst layer formation from a shower nozzle onto a honeycomb substrate, coating the honeycomb substrate with the slurry, and firing the honeycomb substrate coated with the slurry, wherein the viscosity of the slurry at a shear rate of 4 s-1 is 800 mPA·s or less, the shower nozzle has a plurality of discharge openings for discharging the slurry, the relationship of the spacing a of the discharge openings and the diameter b of the liquid drops formed when starting supply of the slurry is 0.85 < a/b, and the equivalent diameter c of a slurry face when starting supply of the slurry and the slurry has spread on the honeycomb substrate is greater than or equal to the spacing a of the discharge openings.