A 73-year-old man suddenly felt severe back pain. Computed tomography showed acute type B dissection. The false lumen existed from the distal arch to the right common femoral artery and was patent. The true lumen was severely compressed by the false lumen and his right leg was cold. In spite of limb ischemia, we started conservative therapy because he had severe airway stenosis due to obesity and obstructive sleep apnea syndrome (OSAS) and we thought surgical intervention very risky. We thought OSAS also involved a risk of high blood pressure and started continuous positive airway pressure. His blood pressure went down along with the improvement of respiratory conditon. After 12 days from the onset he evacuated bloody stool and gastrointestinal fiberscopy revealed giant gastric ulcer bleeding. Platelet counts and prothrombin time began to increase 2 days later. Computed tomography 14 days after onset showed a patent false lumen and severely compressed true lumen. Computed tomography 39 days after onset showed thrombosis of the false lumen and considerable dilatation of the true lumen. Hypercoagulability after bleeding from gastric ulcer and treatment of OSAS were important in this successful conservative therapy.