A casing includes a main body made of a conductive composite material and a local portion located adjacent to a wireless device. The local portion has a non-conductive layer and a conductive composite material layer. The thickness of the conductive composite material layer is thinner than that of the main body that is immediately adjacent to the conductive composite material layer. Signal emitting and signal receiving of the wireless device is not affected by the thickness of the conductive composite material layer of the local portion. The part of the local portion that has a thickness thinner than a thickness of the adjacent main body is installed with the non-conductive layer. The non-conductive layer is tightly connected with the conductive composite material layer of the local portion and the main body that is immediately adjacent to the non-conductive layer.