A method is provided for building an information network via an antenna terminal or an antenna cable disposed in a house for receiving television broadcasting or radio broadcasting. The method comprises step (a) of selecting at least one frequency not used by television broadcasting or radio broadcasting in an area where the house is located; step (b) of modulating a carrier wave having the frequency selected in step (a) by using transmission data transmitted from a first information terminal and transmitting the modulated carrier wave via the antenna terminal or the antenna cable; and step (c) of receiving the carrier wave transmitted in step (b) and demodulating the carrier wave to produce reception data received by a second information terminal.