To provide a structure for supporting tube bundle of a heat exchanger in which it is less expensive and its fixing or removing can be easily carried out.

There is provided a structure for supporting a tube bundle 10 of a heat exchanger 31 in which U-shaped heat transfer tubes 1 arranged in a horizontal orientation are installed in multi-stages to form a tube bundle 10, the tube bundle 10 is connected to an inlet or outlet header 70, and cooling water 5 is flowed in the tube bundle 10 through the inlet or outlet header 70 so as to cool high temperature fluid G flowing outside the tube bundle 10. A number of tube supports 2 formed with notches 3 at both sides in compliance with a vertical clearance of the heat transfer tubes 1 are formed. Each of the tube supports 2 is inserted vertically and arranged between heat transfer tubes 1 opposing in a horizontal direction of the tube bundle 10. The heat transfer tubes 1 are positioned in each of the notches 3, these heat transfer tubes 1 are held by the adjoining tube supports 2 and at the same time cooling water 5 is flowed inn these tube supports 2.