In a method of coating a substrate, inner walls of flow channels of the substrate are coated with a slurry. A plurality of flow channels each opened at both end faces are formed in the substrate. The method includes a step of storing a predetermined amount of slurry in a slurry container in which the end of the substrate, where the flow channels of the substrate are opened, can be inserted under pressure into the slurry container. A step of inserting the substrate with the end of the substrate being downward in the slurry container and dipping the substrate under pressure to the slurry liquid surface, and a step of extending the slurry along the inner wall of the flow channels by blow-opening the respective flow channels in a state of up-turning the slurry container together with the substrate.