A sealing device formed to seal between a fixed side member and a rotating side member, comprising a slinger having a fitting cylindrical part fitted to the rotating side member and a flange part formed at one end part of the fitting cylindrical part positioned on the outer side of a sealed portion so as to be extended in the radial direction. A core comprises at least a fitting cylindrical part fitted to the fixed side member. The sealing device is characterized in that one end part of the fitting cylindrical part positioned on the outer side of the sealed portion is positioned on the sealed portion side more than the sealed portion side inner surface position of the flange part of the slinger and a part of a seal lip part is formed to be projected from near one end part of the fitting cylindrical part of the core and to be brought into elastically slidable contact with the extended end face of the slinger.