Postoperative hemodynamic changes in the aorta in patients with aortic valve stenosis (AS) remain unclear. Four-dimensional (4D) flow MRI was perfumed in 11 AS patients before and after aortic valve replacement (AVR). We evaluated volume flow rate and the main flow direction, setting 15 planes of the aorta and 3 planes of the arch branches. Volume flow rate significantly increased in the ascending aorta and the arch branches. The main flow direction came to match with the axial direction of the aorta. These results suggest that AVR results in more efficient blood transport to the upper body including the brain.