To prevent burglary and theft by transmitting a remote-control conversion code word to a transponder from a transmitter through an interface and storing the conversion code word in a code-word storage device as a new one.

A fixing member is fixed into a car and a diagnostic device is conneced to the fixing member, and an operation method is changed over to the mounting and adjustment of the operation method and a key is inserted into a key switch, and the key switch is operated. A transponder inquiry transceiver receives a command at that time, and a key identification-code word fixedly stored in a transponder receives an inquiry from the transponder, and is stored in a key identification-code word storage device. A remote-control conversion code word is received intermittently in a transmitter while being input into the code-word storage device with the inquiry transceiver and the transponder as a new transponder conversion code word. Accordingly, the burglarproofness of a central locking device with a remote control device can be improved.