Abstract— We have devised a novel type of hand unit that is able to vary its shape for a mobile robot with legs which can be used as manipulation arms to perform handling tasks in a tough field for human such as disaster area, construction site, and so on. Two joint motors are attached at the left and right side of the hand unit to open and close according to the shape of target object. The hand unit was designed and its prototypes were fabricated and attached to the front two legs of a quadruped tracked mobile robot. The experimental results by the robot have confirmed that the developed hand unit increases handling ability of the robot as well as keeping original quadruped walking motion.