A technique is described in which a transistor formed using an oxide semiconductor film, a transistor formed using a polysilicon film, a transistor formed using an amorphous silicon film or the like, a transistor formed using an organic semiconductor film, a light-emitting element, or a passive element is separated from a glass substrate by light or heat. An oxide layer is formed over a light-transmitting substrate, a metal layer is selectively formed over the oxide layer, a resin layer is formed over the metal layer, an element layer is formed over the resin layer, a flexible film is fixed to the element layer, the resin layer and the metal layer are irradiated with light through the light-transmitting substrate, the light-transmitting substrate is separated, and a bottom surface of the metal layer is made bare.