To obtain a tank for integral heat exchanger comprising two tanks coupled integrally in which the tank can be set easily and surely.

The tank for integral heat exchanger where first and second tanks 11 and 13 for heat exchanger are integrated through a barrier wall part 15a comprises an aluminum outer member 15 forming the outer half sections of the first and second tanks 11 and 13 for heat exchanger and the barrier wall part 15a, an aluminum first member 25 forming the inner half section of the first tank 11 for heat exchanger, and an aluminum second member 27 forming the inner half section of the second tank 13 for heat exchanger wherein a part 15h for caulking the barrier wall side 15a of the first and second members 25 and 27 is formed on the barrier wall part 15a.