A method of manufacturing display panels includes forming a material layer on a substrate, and baking the material layer formed on substrate which is placed on a supporting bed. The supporting bed is formed of a first supporting bed and a second supporting bed placed on the first supporting bed. A difference in thermal expansion coefficient between the second supporting bed and the substrate is smaller than a difference in thermal expansion coefficient between the first supporting bed and the substrate, and the substrate is placed on the second supporting bed such that the substrate is positioned entirely within the perimeter of the second supporting bed during the baking and heating. This structure allows reduction of scratches on a surface of the substrate.