Developing a simple and universal solution for gripping fragile, multiscaled, and arbitrary-shaped objects using a robot gripper is challenging. Herein, we propose a universal, shape-adaptive/retaining and reversible, hardness-variable gripper skin that serves as a resourceful solution for grasping such objects without damaging them. The proposed universal gripper skin based on a magnetorheological elastomer is attached to a robot gripper. The proposed skin takes the shape of a target object as soon as the gripper grasps the object. At this time, we solidify the gripper skin by applying a magnetic field, thereby allowing the gripper to grasp the target object easily. After releasing the objects, the magnetic field is removed and the deformed proposed gripper skin rapidly restores its original shape. The proposed adaptive gripper skin is made to grasp various target objects, such as cylinders, cuboids, and triangular prisms, based on which its grasping performance is evaluated.