A gripping device 18 is provided at the front end of an arm of an assembly robot 2. The gripping device 18 includes a pair of grippers 20 and 22 capable of opening and closing. The side configured to come into contact with a part 4, of each gripper 20, 22 includes a pressure-sensitive sensor 24. The pressure-sensitive sensor 24 includes a first electrode and a second electrode serving as a pair of electrodes and an intermediate layer formed of rubber or a rubber composition between the pair of electrodes. The intermediate layer is configured to generate electricity when deformed by contact with an object (part 4). The side configured to come into contact with the object, of the intermediate layer is subjected to a surface modification treatment and has a higher hardness than the opposite side.