A resin material layer including photosensitive resin material is formed on an interlayer on an underlayer. By partially exposing and developing the resin material layer using developer in which the resin material layer and the interlayer are soluble, an uncured portion of the resin material layer is removed to form an opening penetrating to the interlayer, and the developer infiltrates into the interlayer via the opening to remove at least surfaces of first and second portions of the interlayer. The first portion corresponds to the opening. The second portion surrounds the first portion. Each bank is formed by heating a remaining portion of the resin material layer to soften an overhanging portion above a space formed by the surface of the second portion being removed, so that the overhanging portion flows downward to fill the space, cover an exposed portion of the interlayer, and contact the underlayer or the interlayer.