Rheumatoid Arthritis (RA) is an auto immune inflammatory rheumatic disease that can be seen simultaneously in multiple joints, chronic, with an unknown etiology, systemic and clinical course can vary among patients. RA is a type of disease in which doctors have difficulty diagnosing the disease. Early diagnosis of RA disease and knowing the severity of the disease are very important for the treatment to be applied. The diagnosis of RA disease requires physical examination, laboratory tests and medical history of the patient. Laboratory findings to be used in the diagnosis of the disease are not RA-specific and these findings are used to support the diagnosis given according to clinical symptoms or to evaluate the course of the disease. In this study, with the help of a rheumatologist, it is aimed to design a hybrid fuzzy expert system that will help doctors diagnose the disease and support doctors to make decisions for this disease which is difficult to diagnose.