To provide a cleaning brush for heat exchangers capable of safely, rapidly and nearly completely removing the dust accumulated between fins.

This brush is used to clean the fin-and-tube heat exchanger RG installed with many fins F at a small pitch in the outer peripheral parts of pipes P. The brush includes a base plate 1, hair groups 2 arranged in a plural number of rows on one surface of the base plate 1 and a clamping part 3. The front ends of the hair groups 2 are set at the length at which the front ends reach the disposition areas of the pipes P in the state of inserting the hair groups 2 to the max. possible extent between the fins F and F. The fin-and- tube heat exchanger RG is an approximately rectangular parallelepiped body and the plurality of pipes P are arranged between the front and rear parts of the fins F. The hair groups 2 are set at a length at which the hair groups reach the disposition areas of the deepest pipes P.