A low-cost separation method with high mass productivity is provided. A first layer with a thickness of 0.1 μm or more and 3 μm or less can be formed by using a photosensitive and thermosetting material over the formation substrate, a resin layer comprising an opening is formed by forming an opening in the first layer by using a photolithography method, a silicon layer or an oxide layer is formed so as to overlap with the opening of the resin layer, a transistor including a metal oxide is formed over the resin layer, a conductive layer formed in the same manufacturing steps as the source or drain of the transistor is formed over the silicon layer or the oxide layer, the resin layer and one of the silicon layer and the oxide layer are irradiated with the laser light, and the transistor and the conductive layer are separated from the formation substrate.