To make a transmitting and receiving antenna small and to enable long distance communication, even though it is small and light in weight by transmitting and receiving data through a low-orbit communication satellite.

A portable computer A and a portable computer B have the same structure, and both their users are assumed to be in the process of moving. In such cases, when data is transmitted and received between the computers A and B, a network that consists of low-orbit communication satellites N is used. That is, plural satellites N exist on the orbits, go rounds the earth and constitute a network in which communication relay service is always available. Plural satellites which constitute the network separately have a repeater. Data that is transmitted by the computer A is received by the computer B through relaying one of plural satellites. At the same time, data that is transmitted by the computer B is received by the computer A.