SEALING DEVICE

An object is to provide a backup ring manufacturable with an angle of a cut portion set to a standard cut angle even in the case of a product having a small diameter etc. due to dimensional limitation of a device used therewith, and is solved by a sealing device characterized in that a backup ring 1 is disposed in an annular gap 4 formed by disposing a sloped surface 20 on a member surface of one of two members, i.e., a shaft 2 and a housing 3 having a shaft hole in which the shaft 2 is inserted, with a distance from a counterpart member gradually reduced from a high pressure side toward a low pressure side, that the backup ring 1 is in contract with the sloped surface 20 on the low pressure side relative to a mounted seal member 5 made of an annular elastic member, that the backup ring 1 has an axially extending cylindrical portion 10 and a projecting portion 11 continuously disposed on an end portion of the cylindrical portion 10 on the high pressure side and formed to annularly project in a radial direction from the end portion toward the sloped surface 20, and that the projecting portion 11 has a radial tip surface made up of a taper surface 12 facing the sloped surface 20.