A sealing device capable of inhibiting a sealing fluid in an inboard side from leaking to an atmospheric side, comprising: the sealing device having a seal lip with a lip end capable of coming into contact with a shaft and being circumferentially provided in an atmospheric side inclined surface of said seal lip with a plurality of screws which exert a pumping action in relation to said sealing fluid, wherein a three-dimensional shape for preventing the dust from intruding is provided between said screws so as to inhibit the external dust in the atmospheric side from intruding toward said lip end, wherein said three-dimensional shape is constructed by a projection (22; 24; 25) or a groove which extends in a parallel direction to said lip end, wherein said projection or the groove is connected to said screws at each of both end portions (22a, 22b) of said projection or the groove in a longitudinal direction, characterized in that either said projection (22; 24; 25) is formed as a scalene triangular shape having an apex (22c; 24c; 25c) which is arranged closer to the atmospheric side in its cross section such that an elevation angle θ1 of a surface (22d, 23d, 24d, 25d) of said three-dimensional shape arranged toward the atmospheric side of said atmospheric side inclined surface of said seal lip, is set to be larger than an elevation angle θ2 of a surface of said three-dimensional shape arranged toward the lip end side of said atmospheric side inclined surface of said seal lip, θ 1 > θ 2, when the projection is viewed as a cross-section along the shaft axis, or said groove is formed as a scalene triangular shape having a bottom point which is arranged closer to a lip end side in its cross section such that an angle of dip θ3 of a surface of said three-dimensional shape arranged toward the lip end side of said atmospheric side inclined surface of said seal lip, is set to be larger than an angle of dip θ4 of a surface of said three-dimensional shape arranged toward the atmospheric side of said atmospheric side inclined surface of said seal lip, θ 3 > θ 4, when the groove is viewed as a cross-section along the shaft axis. the sealing device having a seal lip with a lip end capable of coming into contact with a shaft and being circumferentially provided in an atmospheric side inclined surface of said seal lip with a plurality of screws which exert a pumping action in relation to said sealing fluid, wherein a three-dimensional shape for preventing the dust from intruding is provided between said screws so as to inhibit the external dust in the atmospheric side from intruding toward said lip end, wherein said three-dimensional shape is constructed by a projection (22; 24; 25) or a groove which extends in a parallel direction to said lip end, wherein said projection or the groove is connected to said screws at each of both end portions (22a, 22b) of said projection or the groove in a longitudinal direction, characterized in that either said projection (22; 24; 25) is formed as a scalene triangular shape having an apex (22c; 24c; 25c) which is arranged closer to the atmospheric side in its cross section such that an elevation angle θ1 of a surface (22d, 23d, 24d, 25d) of said three-dimensional shape arranged toward the atmospheric side of said atmospheric side inclined surface of said seal lip, is set to be larger than an elevation angle θ2 of a surface of said three-dimensional shape arranged toward the lip end side of said atmospheric side inclined surface of said seal lip, θ 1 > θ 2, when the projection is viewed as a cross-section along the shaft axis, or said groove is formed as a scalene triangular shape having a bottom point which is arranged closer to a lip end side in its cross section such that an angle of dip θ3 of a surface of said three-dimensional shape arranged toward the lip end side of said atmospheric side inclined surface of said seal lip, is set to be larger than an angle of dip θ4 of a surface of said three-dimensional shape arranged toward the atmospheric side of said atmospheric side inclined surface of said seal lip, θ 3 > θ 4, when the groove is viewed as a cross-section along the shaft axis.