Disclosed is method of identifying a device that has been connected to a multifunction apparatus to which any device of a plurality of types can be selectively attached, wherein the method makes it possible to prevent malfunction if a device is attached or connected unsatisfactorily. A timing signal for acquiring information that identifies a device is transmitted to the attached device, identifying information transmitted from the attached device in accordance with the timing signal is received, and it is determined, with regard to a device of a specific type, whether specific data contained in the identifying information is indicative of a predetermined value. If it has been determined that the specific data is indicative of the predetermined value, then control is exercised on the assumption that the connected device is that of the specific type.