Etchant and method of etching

An object of the invention is to obtain a fine wiring line profile with satisfactory precision through only one operation of etching a multilayer film containing a first layer made of an aluminum alloy and a second layer formed thereon containing a molybdenum.niobium alloy while etching both the films constituting the multilayer film at the same time and preventing the formation of overhangs of the upper layer film from occurring. The present invention relates to an etchant for etching a multilayer film containing a substrate having formed thereon an aluminum alloy layer and a molybdenum.niobium alloy layer having a niobium content of 2 to 19% by weight formed thereon, wherein the etchant contains an aqueous mixed acid solution of phosphoric acid, nitric acid and an organic acid, and an etching method using the etchant. It is preferred that the phosphoric acid concentration Np is 50 to 75% by weight, the nitric acid content Nn is 2 to 15% by weight, and the acid component concentration defined by Np+(98/63)Nn