The present invention provides a manufacturing technique of a semiconductor device and a display device using a peeling process, in which a transfer process can be conducted with a good state in which a shape and property of an element before peeling are kept. Further, the present invention provides a manufacturing technique of more highly reliable semiconductor devices and display devices with high yield without complicating the apparatus and the process for manufacturing. According to the present invention, an organic compound layer including a photocatalyst substance is formed over a first substrate having a light-transmitting property, an element layer is formed over the organic compound layer including a photocatalyst substance, the organic compound layer including a photocatalyst substance is irradiated with light which has passed through the first substrate, and the element layer is peeled from the first substrate.