To provide a structure to which a member having an automatic exhaust function is added in a cooling water joint for an automobile.

A coupling element 1 for connecting two pipe ends to each other includes: a first connecting end 2; a second connecting end 3; a casing 9 having a connecting water channel 4 formed between the first connecting end 2 and the second connecting end 3; a passage 18 covered with a hygroscopic seal 21; and a ventilating valve 13 including the hygroscopic seal 21, a valve seat 15 disposed in series with the passage 18 and a valve element 14. The valve element 14 is released from the valve seat 15 by pressure in the connecting water channel 4.