In a communication network in which a plurality of equipments each having a function implementing unit having a plurality of functions and a communication control unit having communication function communicating with each other, the communication control unit includes a recording medium and stores on the recording medium in advance a plurality of pieces of function information related to at least one function held by the corresponding function implementing unit, and inquires function information of each of other equipments at the time of communication. Therefore, management of various equipments and function information of various equipments in correspondence with each other becomes unnecessary, load in processing including communication is relieved and functions of respective equipments can be controlled efficiently.