A digital MFP includes a dual I/F storage unit including two different interfaces: an external interface (RFID) and an internal interface (bus). When the power of the digital MFP is turned ON, in steps S406 and S407, if a main controller of the digital MFP determines that license information has been written in the dual I/F storage unit from a portable terminal while the power of the digital MFP was OFF, then in step S408, the main controller validates a function of the digital MFP corresponding to the license information, by using the license information.