A data output system is composed of i) a portable telephone provided with memory for storing data received via a communication line, and ii) an MFP provided with an interface to be connected to the portable phone, for outputting the data stored in the memory of the portable phone, wherein the portable phone includes a display section for displaying received data, and an instructing section for selecting at least one of received data displayed in the display section and instructing the MFP to output the selected data; and the MFP includes a data communication section which starts communication of data according to an output instruction given from the portable phone.