To provide a heat-exchanging device in which an effective hole diameter of a tray through-pass hole where high temperature gas flows can be sufficiently assured.

A tray 6 of an upper heat exchanging chamber is formed by a porous plate in which many through-pass holes 22 with a diameter D being 20 mm are arranged at a thin stainless steel plate having a wall thickness (t) of 2 mm, thereby even if adhering substances 29 composed of adhering substances contained in high temperature gas such as combustion exhaust gas or the like are fixed and grown in the through-pass holes 22, a sufficient large effective hole diameter (d) can be assured.