To provide a low-cost joint eliminated from projecting from a panel and from determining the directivity of the panel when fitted to the panel.

This joint is provided with an outer cylindrical member 9, an intermediate cylindrical member 12 to be inserted in the outer cylindrical member 9, and a seal member 11 provided between the outer cylindrical member 9 and the intermediate cylindrical member 12. This joint is characterized in that a pair of outer cylindrical members 9 are opposed to each other, one outer cylindrical member 9 and the other outer cylindrical member 9 are communicated with each other via the intermediate cylindrical member 12, and the outer cylindrical member 9 and the intermediate cylindrical member 12 can be axially and relatively moved while retaining the sealed state of the interval between the outer cylindrical member 9 and the intermediate cylindrical member 12.