A display device which can prevent a drawback that a positive signal line and a negative signal line are separated to left and right sides of an external connector thus generating impedance mismatching in differential signals is provided. The flexible printed circuit board has a group of differential signal lines including plural pairs of differential signal lines which transmits differential signals, the flexible printed circuit board is constituted of a first portion which includes first connection terminals which are electrically and mechanically connected with electrodes formed on the first substrate, and a second portion which is contiguously formed with the first portion and includes second connection terminals which are connected with the external connector, a pair of GND lines is arranged on both sides of a positive signal line and a negative signal line of each pair of differential signal lines in the first portion and the second portion, and an additional GND line is arranged at least between the positive signal line and the negative signal line of said each pair of differential signal lines in the second portion.