A card key has a molded body and an upper and a lower housings. The molded body has a circuit board, to which electronic parts for communicating with an in-vehicle equipment are mounted and which is covered with resin. The molded body is formed in a plate shape. The upper and the lower housings are fixed to each other so that the molded body is arranged between them. An external appearance of the card key is defined by the upper and the lower housings.