A multi-piece oil ring which comprises: an oil ring main member in which two rails (3, 4) are connected together by a columnar part and which has a roughly I-shaped cross section; and a coil expander which is placed in an inner circumferential groove formed on an inner circumferential surface of the columnar part of the oil ring main member, and which applies force to the oil ring main member in such a way as to press the same outwardly in the radial direction of the oil ring main member; wherein the oil ring main member is made of steel, and characterised in that each of the two rails in the oil ring main member possesses an individual sliding section protuberance (7, 8), a tip of which possesses a jutting portion (9, 10) formed by grinding a portion of the tip of the sliding section protuberance (9, 10); wherein the axial length of the individual jutting portion (9, 10) is in the range of 0.02 to 0.18 mm and the radial length of the individual jutting portion is in the range of 0.03 mm to <0.10 mm; wherein the change rate of the axial length of each individual jutting portion (9, 10) is in the range of 0 to 80% meaning that the value of (X2-X1) /X1 falls within the range of 0 to 0.80, wherein X1 denotes the axial length of the sliding surface to be faced to a cylinder, which is positioned at the tip of the jutting portion; and X2 denotes the axial length of the jutting portion at any given position, at least in a region between its sliding surface which faces a cylinder positioned at the tip of the jutting portion (9, 10) and a position of 0.03 mm away from the aforementioned sliding surface in the radial direction of the oil ring main member; and wherein each portion which underwent grinding shows a concave curved outline in an axial cross-section in the region between its sliding surface which faces a cylinder positioned at the tip of the jutting portion (9, 10) and a position of 0.03 mm away from the aforementioned sliding surface in the radial direction of the oil ring main member. an oil ring main member in which two rails (3, 4) are connected together by a columnar part and which has a roughly I-shaped cross section; and a coil expander which is placed in an inner circumferential groove formed on an inner circumferential surface of the columnar part of the oil ring main member, and which applies force to the oil ring main member in such a way as to press the same outwardly in the radial direction of the oil ring main member; wherein the oil ring main member is made of steel, and characterised in that each of the two rails in the oil ring main member possesses an individual sliding section protuberance (7, 8), a tip of which possesses a jutting portion (9, 10) formed by grinding a portion of the tip of the sliding section protuberance (9, 10); wherein the axial length of the individual jutting portion (9, 10) is in the range of 0.02 to 0.18 mm and the radial length of the individual jutting portion is in the range of 0.03 mm to <0.10 mm; wherein the change rate of the axial length of each individual jutting portion (9, 10) is in the range of 0 to 80% meaning that the value of (X2-X1) /X1 falls within the range of 0 to 0.80, wherein X1 denotes the axial length of the sliding surface to be faced to a cylinder, which is positioned at the tip of the jutting portion; and X2 denotes the axial length of the jutting portion at any given position, at least in a region between its sliding surface which faces a cylinder positioned at the tip of the jutting portion (9, 10) and a position of 0.03 mm away from the aforementioned sliding surface in the radial direction of the oil ring main member; and wherein each portion which underwent grinding shows a concave curved outline in an axial cross-section in the region between its sliding surface which faces a cylinder positioned at the tip of the jutting portion (9, 10) and a position of 0.03 mm away from the aforementioned sliding surface in the radial direction of the oil ring main member.