The yield of a manufacturing process of a display device is increased. The productivity of a display device is increased. A hydrogen-containing layer is formed over a substrate. Then, an oxygen-containing layer is formed over the hydrogen-containing layer. After that, a first layer is formed over the oxygen-containing layer with the use of a material containing a resin or a resin precursor. Subsequently, first heat treatment is performed on the first layer, so that a resin layer is formed. Next, a layer to be peeled is formed over the resin layer. The layer to be peeled and the substrate are separated from each other. The first heat treatment is performed in an oxygen-containing atmosphere.