To easily produce a nano-composite having a periodic crystal structure and to obtain a silica porous body having a large specific surface area.

Tetraalkoxysilane is hydrolyzed under acidity and a soln. prepd. by mixing the resultant hydrolyzate with a surfactant is applied to a substrate and dried to produce the objective silica-surfactant nano-composite having a periodic crystal structure belonging to a hexagonal system and contg. each silica layer enclosing cylindrical micelle formed by the surfactant. The nano- composite is fired to obtain a silica porous body having a periodic crystal structure, ≥1,000m2/g BET specific surface area and 1-2nm average pore diameter. The nano-composite is easily produced and can be obtd. even as a transparent film. The silica porous body is useful as an optical functional material, etc., because of its large specific surface area.