Abstract: Provided is an SD card that can transfer data at a faster speed than a conventional SD card by a data transfer method that is different from a conventional one. Among the four terminals used in the data transfer by the conventional method, respective two terminals are made into pairs. By using the respective pairs of terminals, a data transfer can be performed by the differential signal method. A switching mechanism is provided to switch between the normal method and the differential signal method in a data transfer. When both of the SD card and the host controller with the SD card inserted therein can perform a data transfer by the differential signal method, the data transfer is performed by the differential signal method.