Authentication processing is easily performed on a device used as a node in a network. Upon the authentication of a terminal used as the node in the network, when the terminal can communicate with another terminal, the terminal sends an electronic certificate of the terminal per se to the other terminal and requests the other terminal to perform an authentication process of the terminal per se. Conversely, when the terminal cannot communicate with any other terminal, the terminal outputs the electronic certificate of the terminal per se to an authentication device and requests the authentication device to perform authentication of the terminal per se. The authentication device performs authentication of the terminal based on the outputted electronic certificate.