Alumina-silica-based fiber, ceramic fiber, ceramic fiber complex, retaining seal material, production method thereof, and alumina fiber complex production method

A holding seal material comprising:

• alumina-silica based fibers aggregated into a mat shape as a constituent element, and is placed in a gap between a ceramic body capable of allowing a fluid to flow through the inside thereof and a metal shell covering the outer circumference of the ceramic body, wherein
• a dispersion of fiber diameter in said alumina-silica based fibers is within ±3 μm, and
• a ceramic cross linking bridge comprising a substance made from the alumina-silica based fibers adjoins adjacent ones of the alumina-silica based fibers together in an overlapping area of the alumina-silica based fibers.