The disclosed invention is to provide a semiconductor device enabling it to access an internal device within a USB cable in a simple way. Disclosed is a semiconductor device which is able to be coupled to at least one USB cable and which includes a decision unit that decides whether or not an opposite-end device is detected through the USB cable; and a control unit that, if the decision unit has judged that the opposite-end device is not detected through the USB cable, supplies one of two signal lines which are coupled to an internal device within the USB cable with a power supply voltage and implements control of communication with the internal device within the USB cable through the other one of the signal lines.