To provide a sealing device having improved muddy water resistance while reducing the sliding heating of a seal lip to be generated during high speed rotation corresponding to the axial movement of an inside member relative to an outside member.

The sealing device comprises a side plate 10 to be fitted to the inside member 20 and a seal body 2 to be fitted to the outside member 30. The used seal body 2 is a hydrogenated nitrile rubber elastic body 4 mounted on an annular core 3. The interference of a side lip 7 of the seal body 2 is set to be 0.4-2.7mm, and reactive force due to the contact of the side lip 7 with a flange portion 12 of the side plate 10 is set to be 1.1-2.2N.