This paper presents a 6-DOF manipulator which consists of four parts, 1-DOF translational joint, two 2-DOF bending joints (segment1 and segment2), and 1-DOF rotational gripper. The manipulator with 'flexible shaft and Double Screw Drive (DSD) mechanism' structure can obtain omni-directional bending motion through rotation of flexible shafts. In the first prototype, the flexible shafts were connected directly with the actuators in the manipulator. Compared with the first prototype, in the second prototype, flexible shafts for power transmission are connected to the base of the manipulator. Universal joints are used for power transmission to realize distal motion. The improvement done with the design of the second prototype reduced the torque necessary to drive the flexible shafts during motion in surgical interventions. Experiment results show that the manipulator has enough range of movement for surgical intervention.