Conventional nanocomposites using swelling layered silicates, which are low specific gravity and have markedly improved heat resistance, rigidity and gas barrier compared with talc or mica filling composites, are available. They are, however, much inferior to glass fiber filling composites (FRP) for rigidity and heat resistance if not regarding difference of specific gravity and they may not respond to current high level requirements. The inventors have found that an organic-inorganic composite can be formed by substituting K ions between layers of high-crystalline non-swelling layered silicates composed of mica and having primary particles of large particle size with any positive charged organic compound under specific conditions, leading to completion of the invention which enables production of polymer composite materials having the layered silicates delaminated and dispersed. This organic-inorganic composite is useful as a sheeted filler having a high aspect ratio and the aspect ratio of which further can be increased by dispersing it in a polymer matrix.