Carcinoid tumors are originated from the enterochromaffin cells in the gastrointestinal mucosa. The incidence of rectal carcinoid tumors is more than 10 percent of gastrointestinal tract carcinoid. The tumor has naturally the benign character that does not develop symptoms and it is found incidentally. The tumor may infrequently have a malignant behavior such as invasion to muscle wall, obstruction of bowel lumen and metastasis to distant organ (especially, liver) almost when its size is larger than 2 cm. We have experienced a case of rectal carcinoid tumor smaller than 1 cm in its size with huge metastatic mass of liver.