A mother substrate for a display device includes a display cell, a test pad, an electrostatic preventing pattern and a connecting line. The display cell includes a pad and a signal line. The signal line is extended from the pad and is electrically connected to a pixel. The test pad is disposed out of the display cell and is electrically connected to the signal line of the display cell and receives a test signal. The electrostatic preventing pattern electrically connected to the test pad is disposed adjacent to the test pad and includes a plurality of edges. The electrostatic preventing pattern is formed from a metal pattern. The connecting line is extended from the electrostatic preventing pattern and is electrically connected to the pad of the display cell.