In a flat display panel wherein two plates made of a brittle material are adhered to each other, at least one of the two plates has a plane on which a scribing line is formed, and the plane of the at least one of the plates on which a scribing line is formed is opposed to a plane of the other of the at least one of the two plates on which no scribing line is formed. In one case, the two plates have planes on which scribing is performed, while in another case, only one of the two plates has a plane on which scribing is performed. In the latter case, scribing may be performed on the other of the two plates after the two plates are adhered.