In an external authentication system for a multifunction printer according to the present invention, a USB device management section, according to an instruction from a USB device management section instructing section, (i) performs a virtualization process for virtually connecting an information processing device to a user information reading device which is locally connected to a multifunction printer, (ii) manages a status of the connection between the information processing device and the user information reading device; and a multifunction printer association management section associates the multifunction printer controlled by the information processing device with the user information reading device which is locally connected to the multifunction printer. This allows providing a system in which an information processing device can control a plurality of multifunction printers, and carry out user authentication by controlling, via a communication network, USB devices for reading user information which are locally connected to the multifunction printers, respectively.