The 21st century will see the formation of a "Cyber society" that, while separate from the real world, will cooperate with it, leading to the further expansion and development of world society. Cyber society allows the formation of virtual space through the connection of multiple computers in a network. In this virtual space, multiple users can communicate with each other and can collect and exchange information while moving about freely and engaging in activities. Three main technologies are vital to the construction of the Cyber society : platform technology for converting multimedia information to optical signals and performing digital processing and communication processing on such signals ; communications network technology for transferring these signals from one point to another ; and application technology for configuring the Cyber society that will be formed on this network. This paper describes platform technology and network technology with an emphasis on their relationship to application technology for configuring the Cyber society, and will also discuss interSpace, one of the cyber society platform system of the Cyber society.