To provide the welded tube for a heat exchanger capable of sufficiently guaranteeing air tightness over the whole length of the part abutted and joined with a brazing filler metal and improving quality.

In this tube, an inserting piece 2 and a U shape receiving grooved piece 3 are respectively formed in one side part and the other side part of an aluminum sheet stock 1 with roll forming from the aluminum sheet stock 1 whose surface is clad with the brazing filler metal, the aluminum plate stock 1 is tubularly bent, the inserting piece 2 is inserted into the receiving grooved piece 3 to hold the inserting piece 2 with the receiving grooved piece 3, and the bent arc part 4 of the receiving grooved piece 3 is abutted to the inner wall.