Provided is a method, including: a melting step of melting glass in a melting furnace 2; a distribution step of supplying the molten glass in the melting furnace 2 to a plurality of branched channels 4; and a forming step of supplying the molten glass flowing out from each of the plurality of branched channels 4 to one of a plurality of forming apparatuses 51 to 53 communicating with the plurality of branched channels 4, respectively, and forming the molten glass into a plate-shaped glass by a down-draw method, in which one or more of the plurality of forming apparatuses 51 to 53 are used to form a glass film having a thickness of 1 to 200 μm.