To provide a joint structure of a cylindrical body for a closed conduit to easily improve earthquake resistance of the closed conduit inexpensively.

This structure is provided with a cylinder joint part T composed by putting a pair of cylindrical bodies 11, 11 in which end wall parts Q, Q are recessed in the form of steps to form connection recesses P, P to each other, plural tightening members 12, 12 put over the end wall parts Q, Q set in a continuous condition by the cylinder joint part T, and an elastic filler part 16 composed by hardening mixture of elastic piecess (such as rubber chips) and binder (single liquid binder or the like) and filled and disposed at least in an exposed gap part P1 in a space formed by the connection recesses P, P set in the continuous condition by the cylinder joint part T. When mutualy corresponding opening end surfaces 11a, 11b of the respective cylindrical bodies 11, 11 disposed to be adjacent to each other are put to each other having a gap part W between them, the gap part W may be filled with above mixture.