An image forming apparatus including: a data storage device that stores a user registration information item and/or user group registration information item as address book data; a communication processing section that receives a registration request message described in XML so as to include a plurality of user registration information items and/or user group registration information items; a SOAP processing section that extracts, when the communication processing section receives the registration request message from a client apparatus, each of the plurality of user registration information items and/or user group registration information items that are specified in the registration request message; and a control section that registers the user registration information item and/or user group registration information item that are extracted from the SOAP processing section in the address book data.