We describe two cases of inflammatory myofibroblastic tumor (IMT) of the urinary bladder. Case 1 : A 55-year-old man complained of urinary frequency. Transurethral biopsy of the bladder tumor was performed ; pathological examination revealed IMT. After steroid therapy for 1 year, the tumor was markedly reduced in size. Laparoscopic partial cystectomy was performed. The patient has now been free from recurrence for 3 years after the surgery. Case 2 : A 61-year-old man presented with gross hematuria. Transurethral biopsy of the bladder tumor revealed IMT. Despite steroid therapy for 6 months, the tumor size increased. Laparoscopic partial cystectomy and vesicoureteroneostomy were performed. The patient has now been free from recurrence for 1 year and 11 months after the surgery. IMT of the urinary bladder often responds well to steroid therapy. We experienced two cases of IMT. One showed a good response to steroid therapy and the other showed a poor response to steroid therapy. In both cases, we performed laparoscopic partial cyctectomy and the patients have remained free from recurrence IMT of the urinary bladder may have a good prognosis after complete surgical resection.