To effectively conduct soot blowing over an entire surface of an element by providing a nozzle header driving mechanism for reciprocating a nozzle header, and providing a brake mechanism for holding a position of the header when the mechanism is not operated.

When a soot is blown, a nozzle header 32 is moved at each predetermined amount in a direction substantially parallel to a radial direction of an element by an operation of a driving mechanism at each one revolution of an air outlet side hood 7, and a position of a nozzle 31 is changed radially of the element in association with the movement. Here, while the hook 7 is rotated one revolution after the header 32 is moved, a slider 32 of a brake mechanism 42 projected from the header 32 is sandwiched between slide plates 48 urged by an elastic member 49. Thus, a braking frictional force is operated between the plate 48 and the slider 43, the header 32 is held at the position to prevent a positional change of the header 32.