PURPOSE: To make it possible to connect easily by using a drain pipe and an O ring or only a joint and the O ring and prevent them from coming off firmly and definitely.

CONSTITUTION: When drain pipes 1 are mutually connected to each other, an O ring 3 moves rollingly on a rolling tapered surface, centering on a pipe shaft with fit-in friction force inside an O ring housing recessed part 2 and interposed between the drain pipes 1 at an elastic deformation rate capable exerting a setting force. When a pull-out force is mutually exerted on the drain pipes 1 the O ring moves rollingly on the rolling tapered surface in the pull-out direction with a pull-out friction force, centering on the pipe shaft so that it may be interposed between the drain pipes 1 with a wedge or the like having a large elastic deformation rate.