The present invention provides a precursor composition for forming a conductive oxide film which has high electrical conductivity and in which an amorphous structure can be maintained steadily even when the film is heated to a high temperature, in a simple liquid phase process. This precursor composition comprises: at least one compound selected from the group consisting of carboxylic acid salts, nitric acid salts and sulfuric acid salts of lanthanoid elements (excluding cerium), at least one compound selected from the group consisting of carboxylic acid salts, nitrosyl carboxylic acid salts, nitrosyl nitric acid salts and nitrosyl sulfuric acid salts of ruthenium, iridium and rhodium, and a solvent comprising at least one compound selected from the group consisting of carboxylic acids, alcohols and ketones.