To provide a combined oil control ring with a function of preventing the separate rotation of side rails for a long period of time even under fretting fatigue, seating tabs of a spacer expander are provided with substantially longitudinal projections and recesses on their side-rail-pushing surfaces in a circumferential direction, the width m of a bottom surface being larger than the circumferential length m′ of the top surface in each projection, and a surface connecting the top surface to a recess surface having a bulging shape.