To provide a joint for an inner sub-pipe which can simplify the maintenance of a sewer pipeline in a manhole such as the savings in the visual inspection of the interior of an inflow pipe or time and effort for work.

The joint 10 for the inner sub-pipe is provided with an inflow inlet 28, and side wall surfaces 32 are provided to both sides of the inflow inlet 28. Then a wall surface part 40 is provided by a hinge 38 attached to the side wall surface 32 so that the wall surface part 40 can be detachably attached. Because of this, when the wall surface part 40 is closed, the wall surface part 40 is attached to the front of the inflow inlet 28, and covers an opening 30 of a body. On the other hand, when the wall surface part 40 is opened, the wall surface part 40 is removed and the opening 30 of the body appears. As a result, by the opening of the wall surface part 40, the visual inspection of the interior of the inflow pipe from the opening 30 of the body is made possible, and the removal of the inner sub-pipe becomes unnecessary. Then the time and effort for work can be saved, thus the maintenance can be simplified. Furthermore, when the wall surface part 40 is left closed, a drain of a large amount of sewage into the manhole can also be prevented.