While inguinal hernia is one of the most common diseases, metastatic cancer of an inguinal hernia sac is rare. We report a case of ascending colon cancer metastasized to an inguinal hernia sac. A 60-year-old man, who was undergone a right hemicolectomy for an ascending colon cancer, was pointed out a palpable inguinal mass at one year and eight months after the operation. He was diagnosed as inguinal hernia, and herniorrhaphy was performed. In the operation, a tumor of the inguinal hernia sac, which invaded to spermatic cord, could be found and was removed with right testis. Bassini's method was performed after the resection of the inguinal tumor. Histological examination revealed that the tumor was metastasis of colon carcinoma. Examination of the entire body showed no other metastasis. As for the advanced colon cancer, we need to mention the possibility of metastatic saccular tumor.