Static electricity generated in each data line 3 at the time of manufacturing a TFT active matrix substrate 10 is discharged to a common line 110 through a bidirectional diode 30A. Since the bidirectional diode 30A is configured to have a first allowable level higher than a second allowable level of a protection circuit 112, a leak current that are generated in each data line 3 when being driven is discharged to common lines 111A, 111B through the protection circuit 112.