A 48-year-old woman was admitted to the hospital because of left upper abdominal pain and an abdominal ultrasonography revealed a tumor of the spleen. Colonofiberscope demonstrated a lesion like polyposis at the ileum end, in which malignant lymphoma was found by histological examination. The similar lesion was found in the entire of small intestine by an enteral rentgenoscopy. A preoperative diagnosis of primary splenic malignant lymphoma with metastasis to the small intestine was made by enhanced computed tomography, Garium scintigraphy, magnetic resonance imaging and angiography, and a laparotomy was performed. Exploration of the abdomen showed bloody ascites, a hard tumor in the spleen which appeared over the serosa and a small white nodule on the surface of the liver. Splenectomy, lymph nodes sampling and a patial resection of the liver were performed. Malignant lymphoma was found in all resected materials by histopathological studies. Adjuvant chemotherapy with THP-COP was conducted. There have been no signs of recurrence, and the patient is under clinical observation on an ambulant basis, as of 9 months after the operation.