A liquid crystal display device including, a pair of substrates, a gate electrode of a thin film transistor (TFT) formed on one of the substrates, and a wiring layer connected to the gate electrode or an electrode of the thin film transistor, wherein at least a part of the gate electrode or a part the wiring layer is formed by a layer structured by a pure copper layer and a Cu—Mn alloy layer including Mn, wherein a concentration of Mn in the Cu—Mn alloy layer is more than 0.1 and not more than 20 atomic percentage within a solubility limit of Mn in the copper, and wherein a boundary surface between the Cu—Mn alloy layer and said one of the substrate includes an oxide layer having a Mn oxide layer.