PROBLEM TO BE SOLVED: To provide a treating method of an org. waste capable of recovering a useful material such as phosphorus in an efficient form. SOLUTION: A slurried org. waste is introduced to a solid-liq. separation stage to separate to a dehydrated sludge 3 and a separated water 4. A crushed matter 6 obtained by crushing and fractionating a garbage, etc., and the dehydrated sludge 3 are introduced to an anaerobic fermentation stage and the mixture is fermented under an anaerobic condition to recover a gaseous methane and the generated digested sludge 8 is introduced to a dehydration stage to dehydrate and to recover a dehydrated cake 9. A dehydration filtrate 10 eliminated here is mixed with the separated water 4 and introduced to a dephosphorization stage to dephosphorize by a crystallizing method to recover a phosphorus component as a phosphate crystal 11. A dephosphorized liq. 12 is introduced to a biologically treating stage to subject the dephosphorized liq. to the biological treatment.