An 82-year-old man without notable medical history was admitted to our hospital following subacute deterioration of apettite, disorientation and strange behavior. There was spasticity of the right extremities without weakness. LDH and serum soluble IL2 receptor antibody levels were elevated, and as well as the protein level and IgG levels in the cerebrospinal fluid. CT scanning of the brain revealed a lesion at the left corona radiata. The patient's level of consciousness was worsening, and follow-up study of the brain showed a new lesion in the left occipital lobe. Intravascular lymphomatosis was therefore suspected. We performed a skin biopsy from two typical senile angiomas. In one of these biopsy specimens, a capillary hemangioma was present in the mid-reticular dermis and it was filled with abnormal B cells. The diagnosis of intravascular B cell lymphoma (IVL) was thus established. IVL is a rare subtype of extranodal diffuse large B cell lymphoma with a poor outcome. However, it is recently thought that if the diagnosis is established early, aggressive chemotherapy increases survival. Senile angioma is a skin eruption that is considered prevalent for the most part in elderly people. If a patient is suspected to have IVL, and there is no appropriate site of biopsy, it might be beneficial to try a skin biopsy aiming at senile angiomas for early diagnosis.