A combined oil control ring comprising a pair of circular side rails each having a gap, and a spacer expander longitudinally sandwiched by the side rails, which has seating tabs for pushing inner surfaces of the side rails on the inner side, a side rail-pushing surface of each seating tab being provided with one or more grooves extending substantially longitudinally; each of the side rail-pushing surfaces including the grooves being provided with a nitride layer, and the depth d (μm) of the grooves, the surface hardness h (micro-Vickers hardness HV0.1) of the nitride layer, and the thickness t (μm) of the nitride layer having micro-Vickers hardness HV0.1 of 700 or more meeting the relation of the 0.05≦1000×d/(h×t)≦0.45  (1).