A 51-year-old man was diagnosed as having mitral valve regurgitation( MR). Transesophageal echocardiography revealed severe MR due to A2 prolapse. We decided to perform a mitral valve plasty (MVP). The length of an artificial chord was estimated by measuring the distance from the anterior and posterior papillary muscles to A2 on cardiac computed tomography (CT). The operation was performed with a median sternotomy. The leaflet prolapse lesion was localized in A2, and one torn chord was revealed. Polytetrafluoroethylene sutures were fixed to the papillary muscle, and markings were performed. After fixing the artificial chord to A2 in the predicted length before the operation, a leakage test was performed. We confirmed that the MR had disappeared. The postoperative course was good, and no MR was detected upon postoperative echocardiography. Preoperative prediction of the artificial chord length using cardiac CT is useful because it can be adjusted relatively easily.