A sealing device for sealing space between two members concentrically and relatively rotating comprising a core member fixedly fitted into one of the two members, a metal slinger fixedly fitted into the other of the two members, and an elastic seal member fixedly attached to the core member and having a seal lip which elastically and slidably contacts the slinger. The slinger has a slidably contacting treated surface for the seal lip as is processed such a surface-treatment as defined by the following parameters: arithmetic mean roughness Ra in the range from 0.5 μm to 1.5 μm, root-mean-square roughness Rq in the range from 0.6 μm to 2.0 μm, mean surface irregularity interval Sm in the range from 0.05 mm to 0.17 mm and peak count Pc (50%) in the range from 20 to 60.