A simplified method for forming a pad electrode without using an additional light-irradiation device is disclosed. The method includes forming a gate pad on a substrate, forming a gate insulating layer on a substrate surface, forming a data pad on the gate insulating layer, forming a passivation layer on the substrate surface, forming a first contact hole in the gate insulating layer and the passivation layer, forming a second contact hole in the passivation layer, coating a conductive photoresist on the substrate surface, and forming a gate pad electrode in the first contact hole and a data pad electrode in the second contact hole by ashing the conductive photoresist. The pad electrode is formed in a simple method of ashing the conductive photoresist, thereby decreasing costs.