PURPOSE: To remarkably reduce the probability of the corrosion by providing an exciting mechanism for giving vibration to the inner wall of a desuperheating tower body in which high temperature gas flows.

CONSTITUTION: A desuperheating tower 20 is provided in the flue 10 of the front stage of an exhaust gas treating unit. The tower 20 has a water spraying mechanism 22 for spraying water in a desuperheating tower body 21 in which exhaust gas flows as high temperature gas. The tower 20 is used in the state that the outer wall of the body 21 is brought into contact with the atmosphere 0 of a low temperature part. A speaker 23 is adjacently disposed at the outer wall 21a of the body 21 as an exciting mechanism for giving vibration to the inner wall of the body 21 by means of sound wave. Thus, the water sprayed from the mechanism 22 is reduced at the probability of approaching to the inner wall 21b, and the condensation of moisture is decreased, thereby eliminating the problem of the corrosion.