A method of manufacturing an oil ring is disclosed. The oil ring includes an annular oil ring body having a pair of rail portions at its axially upper and lower portions and butt ends, and a coil expander assembled in the inner periphery of the oil ring body. A number of oil ring bodies and annular spacers having a smaller diameter than the oil ring bodies are stacked, and then aligned and retained using a jig such that an outer periphery of the oil ring bodies becomes a circle. The aligned oil ring bodies are rotated and a flat region that is substantially level with respect to the outer peripheral sliding surface of the plurality of oil ring bodies is formed. Curved regions extending on both sides of that flat region are formed using a buff or an elastic grindstone.