A lock member (16) moves between a standby position, in which a locking part (86) of a locking piece (78) provided on the lock member is placed inside a gap (44) provided between a projecting part (40) and a projecting part (42) provided on a lock part (36) of a connection part (18), and a connected position, in which the locking part is placed beneath the projecting part (42), and the lock member (16) moves to the connected position and is locked by the locking piece (78) when a pipe (12) is inserted up to a prescribed position. Also, an elastic piece (80) and the locking piece (78) are pushed to spread outward and accumulate urging force when being contacted by a flange part (12A) of the pipe (12), but return along an outer perimeter surface of the flange part (12A) and release the urging force when the locked state in the standby position of the locking part (86) is unlocked.