PURPOSE: To simplify the positional alignment between a passage in a branch joint and a through-hole in a main pipe by providing positioning means for aligning the through-hole, the passage and an opening with one another between the main pipe and the joint.

CONSTITUTION: A positioning hole 22 is formed in the side surface of a joint fitting 4, a thread 24 are formed at the outer periphery of a main pipe 1. A planar surface adapted to make contact with a positioning flat surface 23, is formed at the distal end of the thread 24. The main pipe 1 can be fixed to a joint fitting 4 by the fastening the thread 24 while the planar surface is made into contact with the positioning flat surface 23. In this fixed condition, an opening 21 is properly connected to a pressure receiving seat surface 3', and a pressing seat surface is opposed to the pressure receiving seat surface 3' and the opening 21 so that a branch pipe 5 can be connected to the main pipe at a proper position. With this arrangement, it is possible to prevent dust or the like from entering, and to prevent the connected parts from being separated due to vibration.