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This paper presents a load-sensitive continuously variable transmission (CVT) for finger joints. Fingers of robot hands require power when grasping an object and speed when opening and closing. Therefore a CVT is ideal to improve the power transmission of a finger joint. Existing friction CVT are too big and heavy to be installed in a finger joint. By focusing on the fact that finger joints do not necessarily rotate 360 degrees, this paper presents a remarkably simple and small load-sensitive CVT consisting of a five-bar linkage and a torsion coiled spring. Since no special machine elements are necessary, it can be manufactured inexpensively. We have developed a two-finger gripper with the CVT, which can grasp an object powerfully and manipulate quickly.