An Al wiring film having a tapered shape is obtained easily and in a stable manner. An Al wiring film has a double-layer structure including a first Al alloy layer made of Al or an Al alloy, and a second Al alloy layer laid on the first Al alloy layer and having a composition different from a composition of the first Al alloy layer by containing at least one element of Ni, Pd, and Pt. The second Al alloy layer is etched by an alkaline chemical solution used in a developing process of a photoresist, and an end portion of the second Al alloy layer recedes from an end portion of the photoresist. Thereafter, by performing wet etching using the photoresist as a mask, a cross section of the Al wiring film becomes a tapered shape.