A sealing device 1 includes an annular seal portion 5 formed of an elastic material. On an inner peripheral surface of the seal portion 5, a main lip 10 is formed so as to be in slidable contact with an outer peripheral surface S1 of a rotary shaft S, and a vacuum space side inclined surface 11 is formed so as to gradually enlarge in diameter from the main lip 10 toward a vacuum space V side. On the vacuum space side inclined surface 11, a plurality of annular projections 20 are formed along an axial direction so as to be in slidable contact with the outer peripheral surface S 1 of the rotary shaft S in a state where the main lip 10 is in slidable contact with the outer peripheral surface S1 of the rotary shaft S.
