It is provided a method of manufacturing a display device for which the damage caused to the display panel due to processing at high temperatures is reduced. The method of manufacturing a display device includes: preparing a carrier substrate including a surface treated region; laying a mother substrate on the carrier substrate; progressing a process of forming a thin film on the mother substrate; and separating the carrier substrate from the mother substrate by using the surface treated region as an initial separation point. Bonding is formed between the carrier substrate and the mother substrate during forming the thin film over the areas that are not surface treated. The two substrates may be separated by disposing permeating oil on the surface treated region wherefrom oil permeates through the remaining regions by osmotic pressure. This way damage caused to the display panel during thin film processing is reduced.