To establish industrial production to form a quick-acting fertilizer by causing the fermentation of rice bran having a high carbon content and a high fat and oil content in a short period.

The microorganism material for rice bran fermentation is formed by adding vegetable starch and backwheat husk which are hardly decomposable materials to full-ripe bovine dung and causing the aerobic fermentation thereof to increase the densities of Yerscofare (FERM P-17544), Streptomyces canister (FERM P-17545) and Streptomyces prycola (FERM P-17546), by which the enzyme relating to the decomposition of the hardly decomposable materials, such as fibers and polysaccharides, is induced and the decomposition thereof is enhanced. A large amount of natural yeast is thus propagated and the bacteriolytic property of yeasts is enhanced in the late period of the propagation. Further, the microorganismic material for rice bran fermentation is incorporated into the rice bran of ≥20% in arabinoxylane content and water is added thereto to effect fermentation.