To provide a method of promptly manufacturing organic fertilizer by which various kinds of organic residues are finely crushed, the odor of the residues is removed and does not generate during fermentation and aging, the occurrence of foul water is suppressed, and the residues are fermented and fully matured in a short period and recycled to be promptly utilized.

A raw material such a wood residue, animal residue or food residue is charged into a maturing kettle and the boiling point is raised by reducing the pressure in the kettle to decompose the respective residues. A fermentation agent, organic materials and microorganisms which are accelerating the fermentation are added into the respective decomposed residues in the kettle or after discharged from the kettle.