To prevent breakage and the slip of the flexible film substance of arcuate segments, of which an flexible coupling consists, due to a penetrating water pressure during relative displacement in an approach direction between rigid cylindrical members intercoupled through the flexible coupling.

An annular flexible joint 2 consisting of a plurality of arcuate segments 3 is disposed between rigid cylindrical members disposed in water or earth and allows relative displacement between rigid cylindrical members 1a and 1b. Each arcuate segment 3 comprises arcuate frame members 4a and 4b positioned with a distance therebetween and coupled to the rigid cylindrical members 1a and 1b, respectively; a flexible film substance 5 having a side end coupled in a liguidtight state to the arcuate frame bodies 4a and 4b; and air chamber parts 9a and 9b disposed radially externally of the flexible film substance 5 and opened to at least one end of the arcuate member.