A catalyst-aided chemical processing method can process hard-to-process materials, especially SiC, GaN, etc. whose importance as electronic device materials is increasing these days, with high processing efficiency and high precision even for a space wavelength range of not less than several tens of .mu.m. The catalyst-aided chemical processing method comprises: putting a workpiece in a processing liquid in which halogen-containing molecules are dissolved; and moving the workpiece and a catalyst composed of molybdenum or a molybdenum compound relative to each other while keeping the catalyst in contact with or close proximity to a surface to be processed of the workpiece, thereby processing the surface of the workpiece.