A sealing ring used for reciprocating motion and having low friction characteristics. The sealing ring is held at one of two members that move relative to each other and slidably in intimate contact with the other. The sealing ring has an end sliding part having an arcuate cross section and slidably in intimate contact with the other and also has a recessed surface formed in at least either a rear face or both side faces in an axial direction. The sealing ring satisfies the relationships of A/2