To provide a method of manufacturing a catalyst holding seal member which can excellently exhibit restoring force of a fiber raw material and has excellent holding force and sealability.

This method of manufacturing a catalyst holding seal member is characterized to perform following processes in order: a fiber forming process for obtaining formed inorganic fibers by forming an inorganic material (S11); a piling process for obtaining a layered inorganic fiber aggregate by piling the formed inorganic fibers (S12); a burning process for obtaining a burned inorganic fiber aggregate by burning the layered inorganic fiber aggregate (S13); an overlapping process for obtaining an overlapped fiber aggregate by overlapping an organic fiber aggregate with the burned inorganic fiber aggregate (S14); a needle punching process for obtaining a confounded fiber aggregate by confounding organic fibers contained in the organic aggregate with inorganic fibers contained in the burned inorganic fiber aggregate by punching a needle into the overlapped fiber aggregate (S15); and a forming process for obtaining a formed fiber aggregate by forming the confounded fiber aggregate (S17).