PURPOSE: To improve a sealing characteristics of seal devices to be arranged at both surfaces of a heat accumulating core.

CONSTITUTION: A seal device 1 is constructed by a seal plate 11 at a heat accumulating core, a fixed side seal plate 12 and a seal spring 13 sealing between both seal plates 11 and 12. The seal spring 13 is arranged in a multi-stage in respect to a direction where gas pressure is applied. A sliding part 13b at an end edge of the seal spring 13 is movably slid in a parallel direction in respect to a rotary axis of the heat accumulating core 3. A sufficient sealing characteristics can be realized under a labyrinth effect and even if a distance between a seal plate at the heat accumulative core and another seal plate at the fixed part is varied, a superior sealing characteristics is kept only through a sliding movement of the sliding part.