The patient was a 34-year-old male. He visited a community hospital complaining of macroscopic hematuria and pollakiuria. Cystoscopic examination demonstrated a bladder tumor. Transurethral resection of the bladder tumor (TUR-Bt) was performed. Histological examination disclosed malignant lymphoma (non-Hodgkin's lymphoma, mixed type). The tumor was classified into the B cell type by the immunohistological staining with surface antigens. He was referred to St. Marianna University, School of Medicine for chemotherapy. Pelvic computed tomography (CT) after admission demonstrated a tumor with a wide pedicle located in the vesicle triangle extending to the posterolateral wall of the bladder. No abnormalities were found in other organs. After establishment of the diagnosis of primary bladder malignant lymphoma, 6 courses of chemotherapy (adriamycin, vincristine, cyclophosphamide, prednisolone, etoposide, methotrexate) were performed. The tumor disappeared completely on imaging studies after chemotherapy. Biopsy of the bladder disclosed no abnormal tissues. No evidence of recurrence or metastasis was found 5 years after chemotherapy.