To provide a peeling method that achieves low cost and high mass productivity. The peeling method includes the steps of: forming a first layer with a photosensitive material over a formation substrate; forming a first region and a second region having a smaller thickness than the first region in the first layer by photolithography to form a resin layer having the first region and the second region; forming a transistor including an oxide semiconductor in a channel formation region over the first region in the resin layer; forming a conductive layer over the second region in the resin layer; and irradiating the resin layer with laser light to separate the transistor and the formation substrate.