An electronic device includes a USB connector, a power supply unit for supplying electric power to an external device, which is connected via the USB connector, a judgment unit for judging whether the external device is a device being compliant with a USB 2.0 standard or a compatible device being compatible with a device complying with the USB 2.0 standard; and an acquisition unit for acquiring a value of voltage requested by a connected compatible device by communicating with the connected compatible device when the judgment unit judges that the external device is the compatible device; wherein the power supply unit supplies electric power corresponding to the value of voltage acquired by the acquisition unit to the compatible device when the judgment unit judges that the external device is the compatible device.