SEALING DEVICE

PURPOSE: To provide a sealing device capable of realizing the durability of a seal by providing a third sealing member which is made of a resin, separately provided between a protective member and a flange part of a first sealing member, and brought into slidable contact with the flange part and the protective member. CONSTITUTION: In a sealing device 1, an X ring 8 as a third sealing member is made of resin, first and second lips 81, 82 on the atmosphere side A are brought into sealable contact with the end face of a protective plate 7 on the sealed fluid side O, and third and fourth lips 83, 84 on the sealed fluid side O are brought into sealable contact with the end face of a flange part 4 of the first sealing member 5 respectively in a slidable manner to seal the space between the protective plate 7 and the flange part 4. Dusts such as muddy water entering the space 19 from the atmosphere side A are prevented from entering the inside of the sealed fluid side O by the X ring 8, a rubber projection 18A of the flange part 4, a rubber projection 13A of the second sealing member 6 and the second lip 15. The X ring is made of resin, and the wear resistance against the muddy water is improved.