It has been shown that a spatiotemporal map of the intraventricular velocity distribution obtained with the color M-mode Doppler echocardiography reflects relaxation properties of the myocardium of the left ventricle (LV). However, the precise mechanisms are not fully understood. Hence we have carried out a CFD study of the intraventricular flow during an early diastolic phase using a two-dimensional axisymmetic model of the LV. The result showed that the color M-mode images obtained with CFD qualitatively agreed with those obtained in clinical measurements. It was concluded that the intensity and the migration velocity of the vortex that formed in the left ventricle are reflected on the color M-mode images obtained with an ultrasound Doppler echocardiography.