Minimally invasive direct coronary artery bypass (MIDCAB) requires of surgeons precision of hand skill and mental concentration, since it needs to work on beating hearts. We propose a surgical robot system that compensates motions of organs during operations. The motion canceling robot system consists of three technologies; visual synchronization, motion synchronization and master-slave control. The visual stabilization provides the surgeon with the image of stabilized target point on the video monitor. The surgeon operates the master robot referring to the stabilized image. The motion stabilization, on the other hand, controls the slave robot being synchronized with the heart beat, which is the function of the master-slave control. Master-slave transforms the master motion and controls the slave robot. In this paper, we verify the effectiveness of the prototype system by in-vivo experiment.