Primary signet-ring cell carcinoma of the bladder is rare and has a poor prognosis. In addition, there are few successful chemotherapies for it. We report a case of chemotherapy with a docetaxel regimen which was efficacious in a 64-year-old Japanese man suffering from the disease. The onset of bilateral hydronephrosis led to the detection of his bladder tumor, and its pathological diagnosis was signet-ring cell carcinoma(immunohistochemistry showed cytokeratin 7+/20±). He was treated with chemotherapy rather than with surgery because the tumor invaded the abdominal wall and groin. To treat his disease, we performed 2 courses of a chemotherapy regimen comprised of S-1 and cisplatin, but it was not efficacious. We chose docetaxel as a second-line chemotherapy regimen,(60mg/m2, tri-weekly), and a clinical examination including contrast-enhanced CT showed that his disease had successfully responded to the chemotherapy.