To provide a small-sized effective buffer tube which smoothes pulsation in pressure and flow rate in a duct for high-temperature gas which reaches as high as 500 C or more.
The buffer device for smoothing the pulsation of a duct places a side duct 7 which is at the side of ducts 2, 6 and has a large passage cross section. Plate-shaped or concave-shaped rubber thin films 11, 17 formed of thin films with heat resistance and elasticity are placed on its duct end part in an airtight manner. The rubber thin films are deformed into a balloon shape so that the internal volume can substantially change in accordance with the internal pressure, thereby allowing a volume change with respect to the elongation of the rubber thin films to be efficient. A metallic mesh or the like for protecting and restricting the thin films which expand into a balloon shape is placed in an appropriate position inside or outside the duct. This ensures necessary strength, while maintaining an appropriate distance to the high-temperature duct, thereby achieving necessary heat resistance.