A case assembly in a flat display includes a flat display module for presenting a picture; a frame for holding edges of the flat display module; a front case and a rear case for holding the flat display module and the frame in place and fastening the flat display module and the frame together; a first fastening member provided on the front case; and a second fastening member provided on the rear case, wherein the first fastening member and the second fastening member are coupled together to fasten the front case and the rear case.