A sealing device in which a good lubricating oil film is formed along the entire circumference of a sliding surface. The sealing device (1) is fitted in an annular groove formed in either of two elements that are a housing having a shaft hole and a shaft inserted through the shaft hole, and the sealing device (1) seals an annular gap between the two elements. The sealing device (1) has a seal ring (2) sliding against the other element by relative axial movements of the two elements. In the seal ring (2), on each of axially opposite ends of a sliding surface (20) sliding against the other element, there are formed grooves (22) extending from an end surface (21) of the seal ring (2) toward the axial center of a sliding surface (20). Further, in the seal ring (2), the boundary between each groove (22) and the sliding surface (20) is formed only by lines inclined relative to the direction of sliding of the sliding surface (20), and grooves (23) are circumferentially adjacently arranged inthe seal ring (2) so that regions each having the boundary formed by the inclined lines are continuous along the entire circumference of the sliding surface (20).