A 60-year-old man presented at our hospital with gross hematuria. He had been treated for nephrotic syndrome with cyclophosphamide and steroids since he was in his 20s. We detected diffuse hemorrhagic cystitis on cystoscopy and diagnosed him with cyclophosphamide-induced hemorrhagic cystitis. He was hospitalized due to clot retention. We treated him with blood transfusion for severe anemia and conducted continuous bladder irrigation. We performed hyperbaric oxygen therapy and transurethral electric coagulation, and increased the steroid dose. However, we could not control the hematuria. Finally, we performed cystectomy, and he is now well without hematuria. Although cystectomy is the final option, it is important to decide it in a timely manner because a delay decreases the quality of life.