A 15-year-old girl presented to a clinic with an asymptomatic macrohematuria. Cystoscopy revealed a bladder tumor. The next day she was admitted to our hospital because of preshock status with macrohematuria. Abdominal computed tomography (CT) revealed a solid tumor in the left anterior to lateral wall. Urinary cytology was negative. She received a transfusion and transurethral resection of bladder tumor as an emergent operation. Histopathological examination revealed inflammatory myofibroblastic tumor. Anaplastic lymphoma kinase immunohistopathological studies revealed cytoplasmic staining of the myofibroblasts. To our knowledge, this is the 35th reported case of inflammatory myofibroblastic tumor of the bladder in Japan. She has been followed up for 13 months without any evidence of local recurrence.