The congenital bicuspid aortic valve is recognized as a cause of aortic dissection. But in Japan, the case of aortic dissection associated with bicuspid aortic valve is rare. A 66-year-old man was referred to our hospital with a diagnosis of acute Stanford A type dissecting aneurysm associated with stenotic bicuspid aortic valve. The chest computed tomography showed thrombosis of the pseudo lumen. An operation consisting of aortic valve replacement and graft replacement of the aneurysm was performed on emergency basis because of remarkable dilation of the ascending aorta. He has been doing well after the operation and discharged from the hospital on the 46th postoperative day. It is though to be important to follow up with special concern about possible dilation of sinus of Valsalva due to intrinsic weakness of the aortic wall.