A 36-year-old man was admitted to our hospital due to dyspnea and pneumonia. He had undergone left classical Blalock-Taussig shunt at 5 years old and right modified Blalock-Taussig shunt at 16 years old, because he was judged as no indication for any radical operation. Since the last surgery, he had stopped visiting hospital. Computed tomography showed pneumonia and pulmonary embolism in the left lower lung and occlusion of the right modified Blalock-Taussig shunt. After pneumonia was improved by antibiotic treatment, he underwent reoperation of the right modified Blalock-Taussig shunt using 8 mm knitted Dacron graft. Postoperative course was uneventful and dyspnea and cyanosys were improved. We successfully treated a complicated case of an adult congenital heart disease by reoperation of the right modified Blalock-Taussig shunt.