We describe our experience with a patient who had unresectable anal signet-ring cell carcinoma with extensive metastases to the lymph nodes, lungs, and bones. The patient was treated with bevacizumab (Bev)+mFOLFOX6 and achieved complete response (CR). He was a man in his fifties, who visited a local doctor with the chief complaints of swelling in the axillary and inguinal regions. Signet-ring cell carcinoma was diagnosed by examination of a biopsy specimen from the inguinal lymph nodes. A search for the primary tumor was performed, and anal canal carcinoma with pagetoid spread was detected in the perianal region. Positron emission tomography-computed tomography (PET-CT) showed an accumulation in lymph nodes throughout the body, as well as in the lungs and the bones. Bev+mFOLFOX6 therapy was initiated. After completion of 4 courses, the lymph nodes were no longer palpable. PET-CT scanning showed no accumulation. During the 8th course, tumor markers decreased to the normal range, and CR was diagnosed. When 13 courses had been completed, the patient experienced grade 3 numbness of the hands and feet, so his treatment was changed to Bev+FOLFIRI therapy. In conclusion, Bev+mFOLFOX6 therapy achieved 6 months of CR in our patient who had anal signet-ring cell carcinoma with systemic metastases, which seemed likely to have a very poor prognosis.