In a sealing device attached to a housing and slidably brought into close contact with a mating member, the sealing device having a mounting ring fixed to the housing in accordance with metal fitting and a rubber-like elastic body, and having a side lip slidably brought into close contact with an end face portion of the mating member and provided in the rubber-like elastic body, there is provided the sealing device which inhibits a metal fitting portion from being deteriorated due to a rust generation and inhibit inhibiting the side lip from slidably wearing. For this purpose, a flange portion is provided in the mounting ring toward an outer side in a diametrical direction, and an end face portion is covered by attaching an end face seal portion constituted by a rubber-like elastic body brought into close contact with the end face portion of the housing to the flange portion.