Background and Objectives: Valvular heart disease may exert a different influence on left ventricular (LV) function according to the etiologies. The aim of this study was to evaluate the change of the LV function following surgery according to the cause of the valve disease. Methods: A total of 212 patients (50.1짹14.3 years old, 65 females) who underwent isolated aortic or mitral valve surgery (mitral: 152 patients, aortic: 60 patients) were enrolled and divided into two groups: group I (mitral valve group: 152 patients, 49.2짹13.5 years old, 94 females), group II (aortiv valve group: 60 patients, 52.5짹16.1 years old, 25 females). The changes of the LV ejection fraction (EF) were analyzed before and after valve surgery between the groups according to the causes (dominant stenosis or regurgitation). Results: The LVEF was significantly decreased following surgery of aortic regurgitation (60.8짹11.5 to 56.3짹10.5%, p=0.001). However, the LVEF was not changed significantly following surgery of aortic stenosis (61.3짹7.8 to 63.7짹9.9%, p=0.308). The LVEF of patients was decreased following surgery of mitral regurgitation (62.8짹11.5 to 56.7짹12.2%, p<0.001) and the LVEF did not have statistically meaningful change following surgery of mitral stenosis (59.1짹11.0 to EF:58.7짹11.8%, p=0.813). Conclusion: Our study demonstrated that the LVEF was significantly decreased in patients with regurgitant valvular disease following surgery, but not in stenotic valvular disease.