By the selection of the plasma nitriding as a nitriding having a directivity of treatment
without the application of a particular anti-nitriding treatment or of the work removing a nitrided layer, nitriding can be easily applied to only the outer peripheral surface without the upper and lower surfaces and an inner peripheral surface of the compression raschig ring being nitrided. Since the nitriding can be applied to only the outer peripheral surface, in the case that a thick nitriding is applied to a raschig ring which is thin in width and provided with both ends having notches, the raschig ring can retain strength against breakage of a notched portion having a small sectional area in each end. Accordingly, there can be obtained a raschig ring which is thin in width, which has a strength of breakage and which is excellent in wear resistance. Great effect can be obtained particularly in the raschig ring which has a raschig ring width of less than 1.2 mm and a thickness of a nitrided layer of 70 m or more.