To provide a gas distributing valve seal device in a heat accumulative type heat exchanging exhaust gas combustion device having the distributing valve in which discharged gas containing ignitable substances is heat exchanged with heat accumulating material heated by combustion gas and fed to a combustion furnace, a flow of discharged gas to the heat accumulating material and a flow of combustion gas are changed over, wherein the upper section and the lower section of the distributing valve can be sealed concurrently in a superior manner.

Gas flowing into an upper heat accumulating material 2 and gas flowed out of the heat accumulating material 2 are guided by a rotary gas distributing valve. The gas distributing valve is provided with a porous plate 14 acting as a receptor member for the heat accumulating material 2, a sliding upper seal 13 and a sliding lower seal 15. The upper seal 13 is made under a combination of a high hardness seal material for preventing deterioration and wear at a high temperature and a soft cushion material below it, and the lower seal is comprised of a seal plate 20 having a tapered abutting surface and of a soft material 19 to be abutted against the seal member.