The irradiation effect on recovery of organic substances from potato starch wastewater with aid of chitosan and disinfection were investigated for recycling the organic wastes into animal feeds. Chitosan was effective as a coagulant for suspended solids in the wastewater and the optimum concentration was 8-10 x 10 -30/0. The irradiation promotes the coagulation of the organic wastes. Especially, the coagulation of the proteins with chitosan increased by irradiation since the soluble proteins became insoluble by irradiation. The numbers of total aerobic bacteria in the wastewater and in the coagulum with chitosan were 8.0 x 10 7 and 3.5 x 10 8counts/ ml, respectively, and decreased to 11 and 45 counts/ml by 1.0 Mrad irradiation.