A 71-year-old female was seen initially with the complaint of gross hematuria. Cystoscopic examination revealed non-papillary tumor at the dome of the bladder and a transurethral biopsy showed signet ring cell carcinoma. En bloc segmental resection was performed, and the patient has been well without any evidence of progression. We report a case, which we believe to be the 6th in Japan, of signet ring cell carcinoma of the urachus.