A 66-year-old woman complained of dyspnea due to congestive heart failure, and was given a diagnosis of severe aortic insufficiency. Antiphospholipid syndrome and idiopathic thrombocytopenic purpura (ITP) had been diagnosed with 9 years previously. We planned preoperative plasma exchange and steroid pulse infusion to reduce the level of auto-antibodies for phospholipids. The aortic valve replacement was performed safely. Anticoagulant therapy with low molecular weight heparin and oral steroid therapy was administered after the operation to avoid thrombosis or bleeding. The patient's postoperative course was stable. She was discharged without any complication. In conclusion, preoperative plasma exchange and steroid pulse infusion, postoperative anticoagulant therapy and oral steroids resulted in a favorable outcome in a case of heart surgery for a patient with antiphospholipid syndrome.