An etchant for removing an indium oxide layer includes sulfuric acid as a main oxidizer, an auxiliary oxidizer such as H.sub.3PO.sub.4, HNO.sub.3, CH.sub.3COOH, HClO.sub.4, H.sub.2O.sub.2, and a Compound A that is obtained by mixing potassium peroxymonosulfate (2KHSO.sub.5), potassium bisulfate (KHSO.sub.4), and potassium sulfate (K.sub.2SO.sub.4) together in the ratio of 5:3:2, an etching inhibitor comprising an ammonium-based material, and water. The etchant may remove desired portions of the indium oxide layer without damage to a photoresist pattern or layers underlying the indium oxide layer.