A clamping device includes two parts which are pivotably connected to each other by a pivot joint. Each part includes a jaw and a handle. Each jaw has an engaging portion and a clamping portion defined in the inside thereof. A groove is defined in the engaging portion of each jaw so as to accommodate a wire holder. The groove of the engaging portion extends from the nose of each jaw and toward the pivot joint by an angle relative the axis of the inside of each jaw. The groove opens through the nose and one side of each jaw.