Hemangiopericytoma (HPC) arising from within the urinary bladder is exceptionally rare. A 45-year-old man having the symptoms of left groin pain, vague suprapubic discomfort and frequency was admitted to our clinic. Pelvic tomography revealed a tumor in the bladder wall measuring 4 x 3 cm and was not clearly distinct from the lower abdominal wall. Partial cystectomy was performed and the histopathological examination confirmed the hemangiopericytoma. Three thousand rad exterior beam irradiation was performed after operation. Partial cystectomy and adjuvant radiotherapy may be a simple and effective alternative operation for the patient with HPC.