A 1-year-old boy was admitted to our hospital with chief complaint of urinary retention and a lower abdominal large mass. The mass was shown in the bladder by computerized tomography (CT) associated with paraaortic lymph node swelling. Tumor biopsy revealed rhabdomyosarcoma, embryonal type. Complete remission (CR) was obtained by chemotherapy based on STS' 88. He has been healthy 40 months without recurrence. A similar case of rhabdomyosarcoma, embryonal type, in the bladder in a 3-year-old girl with a chief complaint of macrohematuria was verified by CT and tumor biopsy. The same chemotherapy was performed, resulting in partial remission (PR). A complete resection of the tumor was achieved by partial cystectomy. She is alive without recurrence 18 months after the cystectomy.