A seal structure is disclosed as mounted in a coupling 1, exposed in the
vicinity of a stationary member 14, with a dust cover 15 being mounted to
a cylindrical member 19 for preventing foreign material from entering a
gap between the coupling 1 and the stationary member 14, and a seal
member 17 is disposed at a position opposed to the dust cover on the
stationary member 14, with a seal portion 123 of the seal 17 being held
in sliding contact with the dust cover 15.