Eosinophilia is usually accompanied by parasite infestation, allergic condition, drug, collagen disease, and idiopathic hypereosinophilic syndrome. In about 10 to 40% of rheumatoid arthritis patients, peripheral blood reveals eosinophilia. Of the rheumatic disease, eosinophilia may occur in rheumatoid arthritis, sarcoidosis, polyarteritis nodosa and other vascultis. Patient with eosinophilia must be carefully followed up due to possibility of progression to eosinophilic leukemia or myeloproliferatire disease. We experienced a case of rheumatoid arthritis with severe eosinophilia for a period of more than one year in a 53 year-old female patient, eosinophil more than 85% in the peripheral blood, but in spite of careful laboratory study, there was no evidence of parasite infestation, allergic disease and malignant condition that may cause eosinophilia. Therefore we concluded that her severe eosinophilia was associated with rheumatoid arthritis itself, and now she is intensively followed up at the outpatient department. We have to look for any malignant transformation during her clinical course. Marked eosinophilia associated with rheumatoid arthritis is very rare, so we report this case with a review of literatures.