This invention provides a network relay apparatus has an information collecting portion for collecting information about the function and identification of devices V1-V4 in other network n1 through a communication channel N, a virtual unit generating portion for generating virtual unit information corresponding to a first protocol based on the collected device information, and a relay portion which receives a predetermined command from the first network and which transmits the predetermined command to the device in the second network based on the virtual unit information. Consequently, control of apparatuses among networks is facilitated.