Lunch boxes usually contain soft food such as fried chickens and boiled eggs. It is difficult to manipulate soft food objects due to their deformation and variety in shape and size. In this research, we focus on the design of a sensor for grasping such objects using a robot hand. During food object manipulation, a robot hand often applies excess grasping force to the object, causing much deformation of the food, or destroying it. A capacitive force sensor was designed to deal with this problem. Capacitance changes according to the distance between electrodes so, by using this property, a robot hand was equipped with a couple of electrodes are able to measure the grasping force. Some experiments performed showed that the proposed capacitive force sensor successfully detects the change in the force during grasping.