A 27-year-old woman with toxicity of pregnancy and congestive heart failure underwent an emergency cesarean section. In spite of antihypertensive drugs, blood pressure and heart rate were high preoperatively. She coughed many times and SpO2 was 88%. Circulatory state became stable without antihypertensive drugs under combined spinal-epidural anesthesia and continuous intravenous infusion of propofol intraoperatively. After surgery, blood pressure and heart rate became elevated again and congestive heart failure became worse. She was diagnosed as hyperthyroidism by postoperative laboratory examination. If we had discovered her hyperthyroidism, her symptoms of congestive heart failure would not have become worse. We should be more careful about hyperthyroidism in pregnancy because it is not rare.