A high performance sealing device having an excellent pressure resistance and realizing a prevention of damage. The sealing device usable at a working pressure of 0 to 2 MPa, and not damaged even if the pressure of high-pressure fuel of 5 MPa or higher is applied thereto, wherein high pressure fuel on the high pressure side is sealed by a first seal part, oil from a cam side on a low pressure side is sealed by a second seal part, and the fuel slightly leaked due to failure of scraping at the first seal part is sealed by the second seal part to form a dual seal structure. A resin ring coming into slidable sealing contact with a shaft is used in the first seal part, whereby abnormal abrasion does not occur even when fuel having less lubricity is used, and the durability of the seal is increased.