To provide a method for producing organic fertilizer utilizing an organic waste with high nitrogen content and with same shape and fertilizer effect as a usual chemical fertilizer.

Methane gas is recovered by performing both of anaerobic digestion and aerobic composting as pretreatments for drying and granulating the organic fertilizer and used as a drying heat source for drying the organic fertilizer whose moisture content is lowered to 30% or less. Anaerobic digestion sludge containing ammonium is changed to be aerobic by aeration and then a nitrogen component is fixed. A compound to precipitate the nitrogen component such as aluminum sulfate, calcium superphosphate and the like is added to increase a precipitation effect and then the organic fertilizer which contains the nitrogen component highly is produced.