A plurality of first joint tubes 40 connected to a plurality of heat transfer tubes 3 and a plurality of second joint tubes 50 provided at a header 5B are connected to each other at joints J. The joints J include at least one slide joint Ja at which respective ends of the first and the second joint tubes 40 and 50 are fitted to each other slidably in a predetermined direction. The joints J further include at least one butt joint Jb at which an end of either one of the first and the second joint tubes butts against a sealing surface provided at the other one of the first and the second joint tubes. The butt position of the sealing surface and the end is variable in a direction crossing the predetermined direction. With this arrangement, the influence of an error in the arrangement of the first and the second joint tubes 40 and 50 is reduced, so that the header 5B is properly connected to the heat transfer tubes 3 detachably, and the maintenance of the heat exchanger HE is facilitated.