PURPOSE: To provide a process for the storage of grains over a long period while preventing the proliferation of vermin and enabling the proliferation of effective microorganisms.

CONSTITUTION: Grains are stored by mixing the grains with a chitinous substance or placing the grains in contact with a material coated or impregnated with a chitinous substance or placing the grains near a material coated or impregnated with a chitinous substance in separated state. A microbial seed is added to the storing grains beforehand to obtain stored grains containing proliferated microorganisms. A grain-storage bag coated or impregnated with a chitinous substance.