With the evolution of antibiotic agents, necrotizing fasciitis of the male genitalia first described by Fournier has become rare. However, its mortality rate is still high. We present a severe case of this disease. An 80-year-old man who had poor controlled diabetes mellitus was admitted to our hospital with painful swelling of penoscrotal region. Chemotherapy using broad-spectrum antibiotics and drainage of penis, scrotum and lower abdominal wall was performed combined with insulin therapy. Despite the drainage and aggressive chemotherapy with insulin therapy, the gangrene enlarged rapidly and the patient's general condition was getting very poor. Then, we performed extensive debridement including bilateral orchiectomy and amputation of the penis. After the operation, the patient became afebrile and his general condition was improved.