A communication device, includes a CMOS type inverter configured to transfer a signal, the signal being transferred and received between an electronic device and a control part able to communicate with the electronic device whose electric power supply is a rechargeable battery; and a regulator configured to generate a regulated voltage, the regulated voltage being formed by decreasing an electric power supply voltage of the electronic device, wherein the regulator includes a depletion type NMOS transistor where a drain is connected to a high electric potential side of the electric power supply voltage and a gate and a source are mutually connected, and a capacitive element having an electrode connected to the source side and another electrode connected to a low electric potential side of the electric power supply voltage, wherein a voltage of the capacitive element is supplied across both ends of the inverter.