A piston ring comprising: an annular body comprising: an inner circumferential surface and an outer circumferential surface; one side surface and another side surface substantially orthogonal to the inner circumferential surface; and a pair of joint ends (4, 5) opposite to each other to form a joint section, wherein the outer circumferential surface comprises: an inclined surface inclined so as to protrude in a radial direction of the body from a side including the one side surface to another side including the other side surface; and an abutment surface provided toward the other side from the inclined surface, the abutment surface extending substantially parallel to the inner circumferential surface, wherein, in a direction connecting the one side surface and the other side surface, a maximum width W1 of the abutment surface at the joint end (4, 5) is 80% to 150% of a maximum width W2 of the abutment surface in a portion other than the joint end (4, 5), and wherein, in the body, a two-axis difference (d2 - dl) between a diameter dl in a first axis direction passing through a central position of the joint section and a diameter d2 in a second axis direction orthogonal to the first axis direction is greater than -0.25 mm and less than +0.36 mm, characterised in that in each of the pair of joint ends (4, 5), an upper side (12a, 12b) of the abutment surface is inclined with respect to a lower side substantially parallel to the one side surface and the another side surface. an annular body comprising: an inner circumferential surface and an outer circumferential surface; one side surface and another side surface substantially orthogonal to the inner circumferential surface; and a pair of joint ends (4, 5) opposite to each other to form a joint section, an inner circumferential surface and an outer circumferential surface; one side surface and another side surface substantially orthogonal to the inner circumferential surface; and a pair of joint ends (4, 5) opposite to each other to form a joint section, wherein the outer circumferential surface comprises: an inclined surface inclined so as to protrude in a radial direction of the body from a side including the one side surface to another side including the other side surface; and an abutment surface provided toward the other side from the inclined surface, the abutment surface extending substantially parallel to the inner circumferential surface, wherein, in a direction connecting the one side surface and the other side surface, a maximum width W1 of the abutment surface at the joint end (4, 5) is 80% to 150% of a maximum width W2 of the abutment surface in a portion other than the joint end (4, 5), and an inclined surface inclined so as to protrude in a radial direction of the body from a side including the one side surface to another side including the other side surface; and an abutment surface provided toward the other side from the inclined surface, the abutment surface extending substantially parallel to the inner circumferential surface, wherein, in the body, a two-axis difference (d2 - dl) between a diameter dl in a first axis direction passing through a central position of the joint section and a diameter d2 in a second axis direction orthogonal to the first axis direction is greater than -0.25 mm and less than +0.36 mm, characterised in that in each of the pair of joint ends (4, 5), an upper side (12a, 12b) of the abutment surface is inclined with respect to a lower side substantially parallel to the one side surface and the another side surface.