A multifunction device has a plurality of functions selected from among a printer function, scanner function, facsimile function, and data storage function and capable of being connected to a computer via a Universal Serial Bus (USB) interface. The multifunction device includes: a device data outputting unit that outputs information forcing an OS in the computer to recognize the multifunction device as a USB storage class device having a plurality of USB-compliant logic unit numbers (LUNs) when establishing a connection with the computer; and a controlling unit that determines, when output data is transmitted from the computer, which one of the plurality of functions the output data is for controlling, based on the LUN included in the output data, and that controls the determined function based on the output data.