To provide a new organic and inorganic composite material in which aluminum oxide fine particles exist in an organic component while holding thickness in the minor axis direction of ≤5 nm without agglomerate each other with their platy surfaces, and a method for producing the organic and inorganic composite material easily by reacting in a short period of time at a room temperature under normal pressure by using inexpensive inorganic raw materials.

This organic and inorganic composite material comprises at least one kind of organic polymer, selected from the group consisting of a polyurethane and a polyurea, and aluminum oxide fine particles with ≤5 nm minor axis diameter and ≥3 aspect ratio. It is obtained by bringing an organic solution, in which a kind of compound selected from the group consisting of a dichloroformate compound and a phosgene-based compound is dissolved in an organic solvent, into contact with an aqueous solution, in which an alkali aluminate and a diamine are dissolved in water, and reacting them.