The present invention prevents, when a COF which is connected with an external circuit is bent in a flat display device, the disconnection of lines on the COF. At a position where a line of the COF is connected to terminal portions of a TFT, and the line having a large width is branched into lines having a small width T1 to T3 or T4 to T6. By displacing line branching positions from each other as indicated by an arrow A and an arrow B, when the COF is bent or deformed, stress applied to the line branching positions can be dispersed thus preventing the disconnection of lines.