PURPOSE: To prevent generation of thermal strain, obtain a sufficient sliding contact sealing condition and permit to miniaturized a core by a method wherein an annular fluid path is formed in the annular seal member of a high-temperature seal device and a low-temperature high-pressure fluid path is communicated with a delivery path, through which low-temperature high-pressure fluid is delivered from the core, while through this path low-temperature fluid is introduced into and passed through the annular path by a pressure difference between the low-temperature high-pressure fluid path and the delivery path to cool the seal member.

CONSTITUTION: An annular path 31 is formed on the low-temperature side seal member 11 circumferentially so as to be divided while a communicating hole 32, communicated with the low-temperature fluid path 5, and the communicating hole 33, communicated with the delivery path 6, are provided at both ends of the annular paths. When a pressure in the path 5 is compared with the pressure in the path 6, through which the low-temperature high- pressure fluid is delivered after passing through the honeycomb-shape flow path 1A of the core 1, the pressure in the path 5 is higher than the same in the path 6 and the low- temperature fluid in the path 5 is introduced into the path 6 through the holes 32, 33 and the path 33 by this pressure difference. During this period, the seal members 11, 12, especially the seal member 11, may be cooled sufficiently by the low-temperature fluid.