A glass substrate that corresponds to a plurality of product regions and a first grid region that surrounds each of the plurality of product regions and is grid-like is prepared. A protective film that is harder than the glass substrate is formed in the first grid region. A resin layer is formed so as to cover the protective film and the glass substrate. A part of the resin layer is removed by blast processing in a second grid region that avoids the plurality of product regions, overlaps with the first grid region and surrounds each of the plurality of product regions. A circuit layer is formed on the resin layer. The glass substrate is cut along lines that pass through the second grid region where the part of the resin layer is removed. The glass substrate is peeled off from the resin layer.