To provide a joint structure of an immersed tube and a cut-off material for use in the same, which can allow greater relative displacement of the coupled immersed tubes and can ease conditions for an installation location.

A joint part 10 is constituted as follows: primary cut-off rubber 11 is interposed between opposed end faces of the immersed tubes 1 and 2; secondary cut-off rubber 12 is installed on the side of an inner periphery thereof; a coupling steel bar 13 couples both the immersed tubes 1 and 2 together on the side of the inner periphery thereof; and laminated rubber 14 is interposed between both the immersed tubes 1 and 2. The rubber 11 is formed by extending a sealing part 11B which is inclined to one side from a mounding base part 11A in such a manner as to form a prescribed curved surface, fixed to an outer surface of an inside rim part 2B of the immersed tube 2 by the base part 11A, and provided by bringing a pressure contact part 11C at an end into pressure contact with a step part 1C which is formed in an inside corner part of an outside rim part 1B of the immersed tube 1.