A sealing device which is fitted into an annular groove formed in an outer periphery of a shaft so as to seal an annular gap between said shaft and a housing which rotate relative to each other, thereby to hold a fluid pressure in a region to be sealed which is constructed such that the fluid pressure therein changes, comprising: an outer peripheral ring made of resin that is in intimate contact with a side wall surface of said annular groove at a low pressure side thereof, and slides with respect to an inner peripheral surface of a shaft hole in said housing through which said shaft is inserted; and an inner peripheral ring made of a rubber-like elastic body that is in intimate contact with an inner peripheral surface of said outer peripheral ring and a groove bottom surface of said annular groove, respectively, thereby to push said outer peripheral ring toward an outer peripheral surface side thereof; and a portion in said outer peripheral ring which slides with respect to the inner peripheral surface of said shaft hole is constructed by a convex portion (2212, 2212a, 2212b) which is formed so as to extend toward a circumferential direction while changing its position to a high pressure side and a low pressure side in an alternate manner characterized in that due to the formation of the convex portion (2212, 2212a, 2212b), the outer peripheral ring is formed at the high pressure side in its outer peripheral surface with a plurality of concave portions (2221, 2221a, 2221b) which are respectively spaced from one another in the circumferential direction, and the outer peripheral ring is formed at the low pressure side in its outer peripheral surface with a plurality of concave portions (2222, 2222a, 2222b) which are respectively spaced from one another in the circumferential direction, and in the outer peripheral surface of the outer peripheral ring an area occupied by the convex portion (2212, 2212a, 2212b) is narrower than an area occupied by the plurality of the concave portions (2221, 2221a, 2221b) at the high pressure side and the plurality of concave portions (2222, 2222a, 2222b) at the low pressure side. an outer peripheral ring made of resin that is in intimate contact with a side wall surface of said annular groove at a low pressure side thereof, and slides with respect to an inner peripheral surface of a shaft hole in said housing through which said shaft is inserted; and an inner peripheral ring made of a rubber-like elastic body that is in intimate contact with an inner peripheral surface of said outer peripheral ring and a groove bottom surface of said annular groove, respectively, thereby to push said outer peripheral ring toward an outer peripheral surface side thereof; and a portion in said outer peripheral ring which slides with respect to the inner peripheral surface of said shaft hole is constructed by a convex portion (2212, 2212a, 2212b) which is formed so as to extend toward a circumferential direction while changing its position to a high pressure side and a low pressure side in an alternate manner characterized in that due to the formation of the convex portion (2212, 2212a, 2212b), the outer peripheral ring is formed at the high pressure side in its outer peripheral surface with a plurality of concave portions (2221, 2221a, 2221b) which are respectively spaced from one another in the circumferential direction, and the outer peripheral ring is formed at the low pressure side in its outer peripheral surface with a plurality of concave portions (2222, 2222a, 2222b) which are respectively spaced from one another in the circumferential direction, and in the outer peripheral surface of the outer peripheral ring an area occupied by the convex portion (2212, 2212a, 2212b) is narrower than an area occupied by the plurality of the concave portions (2221, 2221a, 2221b) at the high pressure side and the plurality of concave portions (2222, 2222a, 2222b) at the low pressure side.