A sealing structure which is provided with: a shaft and a housing that rotate relative to each other; and a sealing device that is fitted into an annular groove formed in an outer periphery of said shaft so as to seal an annular gap between said shaft and said housing, thereby to hold a fluid pressure in a region to be sealed which is constructed such that the fluid pressure therein changes; said sealing device 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; said outer peripheral ring is formed on its outer peripheral surface with a plurality of concave portions which are spaced from one another in a circumferential direction and which extend from an end of a high pressure side to a position which does not arrive at an end of a low pressure side, so as to introduce fluid thereinto from the high pressure side; and convex portions each formed between adjacent concave portions are formed so as to extend from the low pressure side toward the high pressure side as they go in the sliding direction of said outer peripheral ring with respect to said housing, characterized in that low pressure side convex portions are provided at the low pressure side of said outer peripheral ring, and outer peripheral surfaces of the convex portions and the low pressure side convex portions are composed of the same surface, thus, forming a continuous annular surface. a shaft and a housing that rotate relative to each other; and a sealing device that is fitted into an annular groove formed in an outer periphery of said shaft so as to seal an annular gap between said shaft and said housing, thereby to hold a fluid pressure in a region to be sealed which is constructed such that the fluid pressure therein changes; said sealing device 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; 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; said outer peripheral ring is formed on its outer peripheral surface with a plurality of concave portions which are spaced from one another in a circumferential direction and which extend from an end of a high pressure side to a position which does not arrive at an end of a low pressure side, so as to introduce fluid thereinto from the high pressure side; and convex portions each formed between adjacent concave portions are formed so as to extend from the low pressure side toward the high pressure side as they go in the sliding direction of said outer peripheral ring with respect to said housing, characterized in that low pressure side convex portions are provided at the low pressure side of said outer peripheral ring, and outer peripheral surfaces of the convex portions and the low pressure side convex portions are composed of the same surface, thus, forming a continuous annular surface.