An 80-year-old female patient was undergone sigmoidectomy with D2 lymph node dissection for type 2 sigmoid colon cancer in February 2007. A post operative pathological finding of cancer was SS, N0, P0, H0, M0 (Stage II), curative A. Twelve months after the operation, elevated CEA level was observed. CT scan and MRI revealed a mass of 10 cm in diameter with multiple cysts in the pelvic cavity, which was diagnosed a malignant ovarian tumor. In May 2008, total hysterectomy, bilateral oophorectomy, and partial omentectomy were performed and its pathological finding was metastatic ovarian tumor originating from colon cancer. Adjuvant chemotherapy was administered, as cancer cells were detected in the ascites. The patient has been in good health without recurrence for 25 months after the second operation.