A sealing device includes: an annular seal that is disposed on an outer periphery of a rod of a hydraulic cylinder further on a side of an extending direction than a cylinder head of the hydraulic cylinder and that has a pair of opposing first facing surfaces; a holding member disposed on an outer periphery of the seal; and a fixing member disposed on an outer periphery of the holding member, the fixing member having a tapered inner surface that contacts an outer surface of the holding member and that has an inner diameter increasing toward a retracting direction.