To provide a device for suppressing columnar vibration in a duct in which the columnar vibration can be suppressed with a simple structure without changing the duct placement.

Struts 11 are provided to cross a fluid flow in a duct 10 connected to the outlet side of an induced draft fan 6. The three struts 11 are placed at about the same intervals in the width direction of the duct, and at required intervals in the direction of the flow of the fluid, so that each strut is placed nearly at a part of the vertex angle of a regular triangle.