There is provided a seal ring that makes it possible to improve attachability and sealability.
The seal ring 1 is separated from each other in one area and has a shape with ends, is inserted in an annular groove in a shaft by temporarily moving both the fittable ends 3 and 4 away from each other, and thereby seals an annular gap formed between the shaft and a housing that has a shaft hole into which the shaft is inserted. The seal ring is configured such that: one of both the ends 3 and 4 has a projection 31 projecting in the direction of the circumference of the seal ring; the other end 4 has a recess 42 used in combination with the projection 31. The projection 41 and the recess 42 are fitted together while slid against each other, thereby bringing both the ends 3 and 4 into contact with each other. The seal ring is characterized in that : the recess 42 has an inclining side face 42a, which inclines from the direction of the circumference; and the projection 31 and the recess 42 form a sliding part so that a part of the edge of the leading end of the projection 31 slides over the inclining side face 42a of the recess 42, and portion of the sliding part is formed as a linear sliding portion 13.