A joining structure includes: a first tube made of a first metal or alloy； a second tube made of a second metal or alloy different from the first metal or alloy； a coupling member having a cylindrical shape to provide therein a passage into which the first and second tubes are insertable, and having an opening on a side face thereof to penetrate into the passage； and a brazing material injected into the passage through the opening with an end face of the first tube and an end face of the second tube abutting on each other in the passage to braze the first tube, the second tube, and the coupling member. The second metal or alloy is more easily oxidizable than the first metal or alloy during brazing. An abutting position between the first and second tubes is deviated from the opening toward the second tube.
