A joining device of a continuous conduit is for changes in slope of seabeds. The continuous conduit defines a longitudinal direction substantially coinciding with the longitudinal direction of structural development of the continuous conduit. The continuous conduit has a longitudinal structural continuity and a fluidic continuity. The joining device includes a joint that includes at least one first joining branch, at least one second joining branch and at least one third joining branch. The first joining branch extends along the longitudinal direction and provides longitudinal structural and fluidic continuity of the continuous conduit and connects with a piece of the continuous conduit. The second joining branch provides longitudinal structural continuity of the continuous conduit. The third joining branch provides fluidic continuity of the continuous conduit. The second joining branch is exclusively suitable for providing the longitudinal structural continuity of the continuous conduit, and is unsuitable for providing the fluidic continuity.