We have experienced two cases (Case 1: 21-year-old female, Case 2: 26-year-old female) of systemic lupus erythematosus (SLE) associated with hyperthyroidism. Case 1 had been treated with methimazole (MMI) and betamethasone for approximately two years. Although thyroid function improved with the treatment, laboratory data of SLE deteriorated. She was successfully treated with betamethasone alone. Case 2, who had severe side effect (severe hemorrhage due to gastric ulcer) during prednisolone treatment for SLE, was found to have an additional hyperthyroidism. She was treated with intermittent prednisolone administration alone. Physical findings as well as laboratory data of both SLE and hyperthyroidism improved by the therapy.