A photo-mask having a first exposure area, a second exposure area and a third exposure area is for manufacturing a thin-film transistor substrate. The photo-mask includes a first peripheral line pattern, a first dummy line pattern, a first overlapping pixel pattern and a second overlapping pixel pattern. The first peripheral line pattern is in the first exposure area. The first dummy line pattern is in the first exposure area and connected to the first peripheral line pattern. The first overlapping pixel pattern is in the first exposure area and connected to the first dummy line pattern. The first overlapping pixel pattern is complementary to the second overlapping pixel pattern in the second exposure area. After exposing through and overlapping the first and second overlapping pixel patterns, two patterns respectively formed from exposing through the first and second exposure area are unified.