Orbital metastasis from breast cancer is relatively rare. We report a case of successfully treated orbital metastasis from breast cancer by radiation therapy. This 50-year-old female patient underwent a mastectomy (Bt+Ax) of her left breast in October 2000. The diagnosis was invasive lobular carcinoma, Stage IIB (T2N1M0). Retroperitoneal and bladder metastases were found five years after the operation, and chemohormonal therapy was done. Right orbital swelling appeared 8 months after chemohormonal therapy, and orbital metastasis from breast cancer was diagnosed by MRI. Radiation therapy (a total 30 Gy) was administrated, and the swelling disappeared. An MRI was performed 16 months after radiation therapy and did not detect any metastases. A complete response (CR) was achieved. No sign of recurrence was found, and a sufficient local control has remained for 2 years after radiation therapy.