Continuum manipulators are widely used in surgical robots because they can reach difficult-to-access surgical sites via complicated pathways using their flexibility, small size and agility. However, shape-distortion and deflection problem caused by their redundancy adversely affect payload handling and grasping performance of surgical instruments consisting of redundant joints. To overcome these problems, many studies related to design optimization of surgical instruments with redundant joints is being conducted. However, there are not enough researches about comparing and analyzing the operational performance of surgical instrument according to the number of joints. In this paper, experimental analysis of the effect of the number of redundant joints on operational performance of a surgical instrument is conducted. Two surgical instruments with four and six redundant joints each were compared in terms of payload, grasping speed and force. As a result, the results show that the surgical instrument with four joints are better in terms of payload and grasping performance.