A 60-year-old woman with extensive hematuria visited our hospital. Cystoscopy revealed a tumor with an edematous surface on the left lateral wall of the urinary bladder. To diagnose the tumor, we performed a transurethral resection of the bladder tumor. Pathological examination suggested leiomyoma. Four weeks after the transurethral resection, magnetic resonance imaging revealed an increase in the bladder tumor. She received partial cystectomy. Pathological analysis revealed an inflammatory myofibroblastic tumor. No recurrence was observed 9 months after the initial operation.