To provide a method for preparing a storage material comprising a light weight carbonaceous material readily available at a low cost having an excellent capacity of storing, releasing or adsorbing a gaseous monomer, or adsorbing a liquid monomer, or adsorbing a microorganism or a microparticle, which carbonaceous material is capable of storing a useful gas dangerous for storing in particular.

The method for preparing a carbonaceous material for use in storing, releasing or adsorbing a gaseous monomer, or adsorbing a liquid monomer, or adsorbing a microorganism or a microparticle comprises steps of treating raw cotton with sodium hydroxide and subsequently treating the raw cotton with a strong acid or comprises the step of treating cotton wool with an acid, whereby the bondage of cellulose fibers is chemically loosened and the raw cotton or the cotton wool is carbonized.