We experience a case of 34-year-old Turner's syndrome(45, XO) associated with atrial septal defect(secondum type) and mitral valve prolapse who was admitten due to moderate exertional dyspnea. It is well know hat chromosomal abnormality is one of the etiology of congenital heart disease. In case of Turner's syndrome, coarctation of aorta or bocuspid aortic valve is frequently combined, but atrial septal defect simultaneously with mitral valve prolapse is not reported till now in Krea.